Not sure I 100% understand what you want to do here but as for the mechanics of it, it sounds like you want to remap the controller and because it’s not capable from the manufacturer, you have to do so using a secondary device.
I know that something like Blokas midihub or Plexus midi router have some ability to do what you want but really not sure about resetting to 0 on release or how many mappings are possible to a single device.
You might be able to ask Joe @jmkmusic about specifics of Plexus, although it’s possible someone else who is using one might know these answers as well.
Not sure who would be able to confirm about the Blokas midihub, I know some people here are using it but have not heard of it being used like this specifically.
I believe the price of these devices is probably in line with metaconformer so this may be the wall that you’re up against price-wise.
I have no idea about ipad but you may want to check out that thread from a while back about ipad apps for music, I’ll have to look for it because I don’t remember the title.
Ah, I found it, this is the ipad app thread that I was thinking of:
Anyway, good luck. Hope you figure it out.