Hello Jason - Wow! Full circle - they've been building synths to emulate pianos for decades - now they're building pianos to emulate synths! I'm still waiting for the 'Star Trek' piano that you roll up and stick in your pocket ...

The transacoustic piano was first unveiled in 2013 and later released officially in 2014 - so it's not brand new (just a newer, even larger model, now). The most realistic keyboard action will probably come from this sort of thing that is actually an acoustic piano. And sympathetic string resonance can come from actual strings vibrating actual wood - so no need to really model that when using a transacoustic assuming the dampers still can lift up (disengage) while in digital mode and the hammers are disabled.

It would be kind of cool to have perhaps one with a tiny soundboard that runs under the keys - about the size of a Rhodes 88 Suitcase (but taller because of the soundboard) - short strings instead of tines - and some form of real hammer - maybe plastic with non-traditional hammers. So it'd still be wood - still heavy (but light enough to still carry to gigs with a dolly) - and a real mechanism with at least Rhodes-like action if not fully acoustic piano action.

I guess a no-string "grand feel" (Kawai) style action would be OK - but no acoustic string resonance.