After discussing the TK2 issue with Nasta, I'd like to add the following:
TK2 would not have problems in OUR RAM expansion because it works as fast as ROM does
This works even for the 512k version as long as TK2 is LRESPRed. For the 896k version with internal RAM speedup, it does not matter - code will run at maximum speed anywhere, even if loaded into the screen
The 896k version will contain 32k of RAM at $10000..$17FFF unless the peripheral relocation to $10000 is activated (in this case it will have 16 of RAM at $14000..$17FFF). This can be used to emulate ROM, a ROM image (or two in case the full 32k is available) in there will be initialized by Minerva. It also survives reset since it's SRAM, and will keep the contents as long as there is power.
There will also be a plentiful supply of Minerva upgrades which also contain TK2.