For me, it would depend on the action, controls, I/O, and price.
I agree they could make the most playable digital piano on the market if they partnered with the right manufacturer, but it's already really convenient (as Key Fumbler noted), to run Pianoteq without a laptop/desktop computer. Even more so if your digital piano has an integrated audio interface, as most manufacturers are now including.
If you don't have an iOS device, lots of folks have built some creative solutions using Raspberry Pi or similar small form-factor Linux devices that can be easily attached to the digital piano and hidden from view if desired.
Don't get me wrong, if I could swap out my keyboard for something with nice tactile controls tailored specifically to Pianoteq, along with some premium key action and a synth engine on par with something like the Nord Stage series, I'd consider it (depending on price).
Right now, if I want to play without a computer, I just connect one cable to my phone and I'm all set. Not a lot of friction for me, especially compared to the risk of buying an action I likely wouldn't be able to try for myself before purchasing.