Ross,
Virtually everything is possible with the Gigacontrol software. Even complex mixers from one channel to other ones.
Take some time to read both user manuals for the 35/72 Mhz units and 2.4 units. You won't regret the time spent.

You can offset the neutral for each servo by moving the whole curve.

A well programmed 12-22 units is nearly impossible to saturate. However the multiplex functions from Futaba/Graupner will soon be supported with will potentially increase the inputs to 26 channels an outputs to 36 servos ( 44 with the 12-30 unit ).