On the FM9 you could use eight amps gaplessly in a preset if you’re willing to stomp twice. Use two amp blocks, with a different amp on each channel, in front of a Multiplexer. While you’re on one of the channels in Amp Block 1, select the channel on Amp Block 2 that you’d like to switch to silently; then, when you’re actually ready to switch amps, use the Multiplexer to switch to Amp Block 2 gaplessly.
The obvious limitation is not being able to switch between channels on the same block gaplessly, but this still means four gapless amp switching potentials at a time. Throw in gapless Scene Controllers, and another Multiplexer block for gapless drives, and you've got an enormous potential for gapless switching, well beyond reasonable for any live situation, I think.
Note: with Scene Controllers you must reduce damping parameters: modifier attack and release to zero, and update rate to fast.
On the FM3 you still have one Multiplexer Block that you can run with two Drive Blocks. Run a different model for each drive channel and you can get wildly different gapless tones. Plus, you still have Scene Controllers on the FM3 too, so there are still so many gapless options on that unit.
