Actually, I was thinking of the LFO too yesterday, but in a slightly different way: I would like to increase its rate for sure, but then would also like to have either a second LFO route to its frequency or, perhaps even better, an envelope.
In some configurations, the Arp signal, the PWM Speed and the Effects Speed oscillators are lying unused, so I wonder if this can be tapped into.
I may do initial tests with on-board secondary (LF) oscillators driving the MG LFO and then wire in my own using the Arduino. I only have a UNO and not a Mega, so I'm a bit limited in the kind of performance and synthesis mods you effected (brilliant set of mods, by the way) for now.
Another way for more flexibility would be to do a CV-in for the LFO speed, which would let me wire in either the Arduino or Expert Sleepers' Silent Way. How feasible is this and what is required apart from a jack?
Coming back to the FM mod you suggested, this is very good and could also be used with the ones above. The question is: will we be able to get a good musical tracking in an easy way with the FM across the keyboard. Otherwise, we can still use the mod for FX sounds.
I can see Radek's mods around the Mod Wheel and LFO in the Photos section. Johannes's kit/mod file also describes some mods there, so that could be envisioned too.