For an electric guitarist to solo effectively on an acoustic...

For an electric guitarist to solo effectively on an acoustic guitar you need to develop tricks to avoid the expectation of sustain that comes from playing electrics. Try cascades, for example. Drop arpeggios over open strings, and let the open strings sing as you pick with your fingers. It's kind of a country style of playing, but it works very well in-between heavily strummed parts and fingered lead lines.