The Conductor can be used to do all sorts of things such as Start/Stop play, loop, jump to a particular chorus. You can customize keys to do additional functions. It also has a feature to mute/unmute parts with the computer or Midi keypress. Check out the Conductor, you may find some things very handy to your situation.

As far as your soloist need, the only way I can see that happening is by using Mute/Unmute on the Soloist part. You could generate your solo on a part, and then mute/unmute when desired.

R