Embodme

The above-two things are improvements worth carrying over from existing tech in the field that a future Touch could specifically benefit from.  I realize that you're not trying to "be an electronic drum manufacturer" per se, but incorporating the above-two mentioned features would make your product a V-Drum killer for at least single-pad considerations.  We can go further than this though...

The playable rim should be thicker (horizontally) in size than the V-Drum rim, because the Touch instrumentalist is not playing on what tries to convey a real drum (like Roland is), and so it doesn't make sense for the rim to be narrow in the V-Drum style.  Making the rim the same height as the V-Drum rim (or at least most of the way there) would still be useful for drummers who know what a cross-stick should 'feel' like.  Because the very nature of your pad crosses the boundary between melodic instrumentalist and drummer, having a thicker rim than the one on the V-Drum (horizontally thicker, and more 'oblate' in shape) would improve sticking accuracy at the rim for less experienced drummers.  Jazz artists should be able to cross-stick, and marching percussionists should be able to shot/gock, reliably in both cases.

For the purposes of improved drumming at the rim: it may make sense to have the whole top view of the pad shaped to be even more ovular when compared to the present "squoval" shape of the Touch.  The slight shape adjustment towards 'more curvy' would make cross-sticking and shots feel more authentic, giving the drummer an unequivocal full range of expression on the Touch.  The rim should feel 'stiffer' than the rest of the pad's playable surface to more correctly provide the expected sensation while playing, and to ensure to the drummer by 'feel' that it's a proper rim capable of receiving the naturally-heavier strike weight associated with cross-sticks and shots / gocks. Because the rim would have multi-sensors like the pad itself - the virtual representation of the hardware buttons should be repositionable / strikable along the rim as any other configurable virtual control on the Touch.  Imagine a right-handed person being able to play hi-hat all over the left rim (with their right hand) while crisply cross-sticking the right rim with their left ...and then a left-handed person being able to do the exact same thing with a flipped config of the trigger scene.

It's subtle, but the existing Touch's physical button panel could leave a bit of a nagging sensation in the back of a drummer's mind while they're playing like they'll accidentally strike it when "going wild" musically and break an important (or crucial) feature of the pad.  As such it makes sense to decouple the physical buttons from the playing surface, so why not make the button panel part of its own module that's able to swivel around a "groove track" in the bottom of the pad, secure it into position somehow, and then 'telescope' a harness via a bit of hardware into whatever position / distance away from the rim feels most comfortable to the player?  This telescoping button panel should be hinged in such a way as to be collapsible where it slides into a bottom storage panel seamlessly for when the player's on-the-go (preserving the pad's aesthetic and notion of compact travel).

During play sessions: the button panel and its hinge should even be entirely removeable from, or simply stored within, the pad.  This is when the musician wants to instead strike the virtual representations of those buttons on the pad itself during a sesh.  The hardware buttons would live on a thin, simple button remote (think 'thin' like one of those little LED remotes).  It would snap in & out of the telescoping hinge harness (securely), and the hinge's strength and structure would also allow for the safe/secure snap-in of a thicker smart phone into the hinge's harness, where the player would then use an embodme phone app instead of the hardware button panel.  The future Touch would need to implement Bluetooth and provide a pairing button on the bottom for both the button remote and for a phone.  The supplied (and future) remote(s) would need to have a user-replaceable battery that's chargeable from the Touch's USB port, where the remote is still useable during charge cycle.

A separately purchasable, upgraded 'sibling' hardware remote may be worthwhile to create for players who wish to have even more sophisticated control over their sesh via remote, but don't want to use their phone (think DAWless players wanting to "get away from phones / computers").  The upgraded remote might (for example) be an even thinner, decently sized color touch screen device that provides all the core features as the phone app while remaining 'gently' future-proofable via firmware upgrade.  I say 'gently' because not a lot of extra future functionality can be expected to make it to a "thick credit-card" remote which is not as powerful as a modern phone, but which still must fit inside a narrow slidable compartment on the bottom of the Touch (along with its hinge harness).  If the user wants more remote functionality than either the original "thick credit card" panel or the separately purchasable upgraded one I mentioned, then they'll just have to get the full version of the app for their phone to handle it.

That being said, a next iteration of the Touch which incorporates a storable hinge harness and button remote should have its bottom panel structured in such a way as to accommodate the size of the largest diagonal-width version of either button remote on offer, as well as the slightly smaller version of the (other) button remote, so that the initial users will already have enough physical storage space for an upgraded button remote in the bottom of the future Touch.  The bottom storage compartment would also need to be engineered in such a way as to ensure that the slightly smaller version of the button remote doesn't "slide around" noisily when the Touch is in transport, allowing secure storage for either remote option.  This may mean having a 'tiered cut-out' in the bottom housing to safely store either panel, where the thicker panel is the smaller-diagonal one, and the thinner panel is the upgraded touch-screen one which is larger-diagonal.  The player's phone will just have to be stored in their pocket or purse as before, because it would make the Touch too thick to store a thick phone like that.

The replaceable drumhead feature would require providing the user with a bit of self-maintainable freedom whilst still allowing their Touch to remain under warranty.  The user would have to be responsible for knowing how to remove the rim trigger from the Touch in order to access the head for replacement, and then the design would need to allow them to easily replace the rim once they've replaced the head.  As such, both the rim and the head would probably need to be developed as a 'snap-fit' type of tech in order to not be forced to incorporate normal drum lugs in the design for head tightening like Roland does.

Hardware decoupling to allow the replaceable head, adding on the drummable rim, and allowing the button panel to positionally 'satellite' around the pad in a detachable remote control (or via the app on their phone) would give the user even more confidence in playing the Touch however they want.  They'll know they can rely on the ruggedized nature of the musical instrument upon which they're being creative, even when getting crazy with heavy marching sticks (doing 'gocks' etc), because they'll not be able to (easily) strike either the physical buttons and will no longer have to avoid the pad's (far) edge during performance.

Making the Touch more modular in the above ways would give even more confidence to the prospective client that they'll be able to enjoy their pad long-term due to the availability of replaceable parts should things go awry. De-coupling the playable surface from the electronics in the above-mentioned ways also makes sense from a warranty-support perspective, because it's way cheaper to just send out replaceable button panel remotes, heads, and even a rim if needed ...that it would be to send out a whole new system when either the buttons or head (or rim) are messed up. The satelliting button panel would also provide more ease-of-use for left-handed people who might prefer physical buttons to their right or elsewhere.

If needed, I can (roughly) mock-up a few of these things in an art program when I'm freer, just let me know.  Like I mentioned I'm going to buy a Touch regardless because it's such an amazingly flexible piece of gear, but thank you for considering a model with the above features :)