It would be great if the sustain pedal could be set to sostenuto mode. This would work differently from the regular sustain mode as follows:
(1) Hold some notes down
(2) Hold down the sustain pedal
(3) Only the notes that were held when pressing the sustain pedal will be sustained and any subsequently played notes will NOT be sustained.
This would allow one to sustain a chord with the pedal while then playing a lead over it, leaving a hand free to use the expression controls.