What I plan on doing is, buffering the 32mhz clock first of all, then inverting it for the MMU input. So that means lifting the 16mhz output of the shifter and replacing that line with the new inverted 32mhz clock. That should match what you have.
Then the 4mhz output of the MMU will have to be cut, I am assuming here that the only thing on the 4mhz line is the MFP. So I will probably lift that pin on the MFP itself and feed that via a flip flop to downclock it back to 4mhz.
I have ordered some 2mhz ACIA's, though not arrived yet

The last mod will be the DE mod. There it looks like a track cut needed to the MMU and as you pointed out, it must be pin 54 not 52. So we feed in the GLUE 2mhz clock.
I have a ST *somewhere* with a 4MB simm adapter all ready to go. So Hopefully in a few days I can have this mod built so I can do some testing


Incidentally, my Lattice programmer has come, so "at some point" I will program my clock sync circuit to see if I can get out of sync clocks working to try any mhz speeds. Though this is a lot of work so will take some weeks to complete overall.