I'll get to MPU5 eventually, but there are better techs to emulate first.
From a brief look at the source, the Switches are read via the ASIC. The ASIC can be varied from game to game so I would guess it has something to do with that. Not much chance of a workaround in MFME as it stands.
The current plan (briefly) is this...
1) Get Epoch/Impact working 100% with the editor and release it.
2) Find all the bugs that crop up once it goes live.
3) Except for super critical bugs which will get an asap update, after 2 weeks or so release an updated version with the fixes in, and hopefully regular MPU4 as it's already 95% written and ready to go but needs altering in some ways to suit Amber2, rather than Amber1.
4) Once those 3 techs are bug free and stable, start work on MPU4 Video, & Plasma, closely followed by Castle.
Once I have those 6 techs done, I'll then see how to proceed.