Nice! The keyboard controller on the P30 is a NEC D8741AD. I'll ask in the German forum for software to try in the P30 emulation.
Is it possible to allow split screen for the graphics extension like on the Rainbow driver?
Not without some difficulty as there's not really any simple way to bind two screens to one crtc. Note the graphics extension still doesn't work properly, that shot is with disdeu.sys disabled.
If possible, we should get a dump of that MCU.
It's dumped and emulated. Also, the P3 driver has a dump of the 8278 (which is an 8041 with a standard program) so if there are any other drivers that use an 8278 but lack a dump of it, that one should be just able to be dropped in.