the control of the peaking amplifier is probably best done by a fast DAC controlled by calculated modulation envelope, but with modern practice being heavily DSP based it looks to me to be possible.
I think this probably sinks a lot of ham experimentation...
You're one of the few people I've ever seen in a web forum who has access to the signals needed control what you're suggesting.
A lot of the high efficiency amplifier ideas out there aren't really suitable for add on amplification of SSB or sometimes even CW. If you build the whole transmitter, like I know you have and like the mobile phone people are doing, you can do something reasonable.
I don't have any good direct leads for you. You probably already know XQ6FOD's page but if you don't, you might want to dig around there for a while...http://ludens.cl/Electron/mosfetamps/amps.html