I had this idea as well a while ago; even if i got such a piece (QY-10) i didn’t liked the way it sounds and the way it BRAIN was in a decent way limited.
I also owe an electribe EM-1 (and yes, i’ve time to go here and read… ;D…neary impossible…)
In the electribe community there’s a very great interest to make their babys mobile…nothing to say against it but batteries are heavy… someone managed it very elegant with an RC-Car batterykit to get it working for 4-5 hours!!! (to be amused on his business flights)
BUT: if someone doesnt like the OS anymore - there’s no chance to get another…and there will never be a chance to change it by yourself! chameleon and other products (a dedicated PC based Workstation/Synth or a vst-based PC based multieffect 19" platform, sorry lost the names somewhere ;D) are very seriously products of the future, well reviewed by the progressive recording studio community.
Think of PIC based hardware platforms like a:
- Mobile MIDIb*x (SMD type style with LF pic)
(with small chip synth inside?)
or
with some very DIFFERENT OS’es (pattern seqencing, midi recorder/looper, step seq, drumbox…), scalable to the hardware platforms
but with compatible exchange format (sysex unified, exchangeable banksticks…)
This all is already possible with the mios platform -
it’s all up to the design
I really would like to have “mobile” dedicated simple little midi machines, some more of them, capable to act as a modular midi system, where every PIC Module can be loaded with all kind of MIDI sysex progammable apps like sequencer, arpeggiator, (one minisyth module), midifilter, splitter/merger, harmonizer, scaler etc in small boxes ready to be docked togeter (in analogy to analog modular systems) with a midi lag smaller than cubase 
