Would be neat if the Peavey MuseBox ran Pianoteq. I wonder if anyone has hacked it yet to run whatever VSTs you like. I have a strong suspicion it's possible to do that - for any Receptor actually. I just did a search for "hack muse receptor", found a few links but nothing substantial. Maybe the market for interested Linux guys isn't big enough.
That said, my second choice would be a Mac MINI with a small touch screen LCD monitor. There are lots of solutions for hanging a Mac MINI on the back of a monitor. clonk
touch-base.com keeps a running list of touch screen monitors that work with their drivers for OSX.
Apple already made MainStage. Done.
Heck, I like this idea so much, I might do it myself.
If you're a Windows guy, a NUC might do the trick for VSTs with the right host.
NUC mount, clonk.