So, exactly why would an iPad be useful but not, say, some random other tablet, my windows phone, etc? I also disagree with the idea that the app would need custom scripts, necessarily... One can imagine having any application on computer 1 (i.e. phone, tablet, whatnot), communicating with application on computer 2 over virtual midi. The application has configurable buttons, (e.g. 'rightclick to name button') and configurable output (e.g. 'rightclick to set output channel' &c). This would make it unnecessary - though one could easily add such - to have custom patches as your iPad or whatever will be just a fully customisable midi controller - basically one for which you need no stickers! It would, after all, be quite odd to have such an extremely adaptable piece of software as VI(P)/VE(P) and then suddenly be stuck with someone else's keyswitch schemes!
Sorry - ending rant here. All in all, I also really want a touchscreen tablet computer, call me jealous!