@Omnicron You make a point about SuperCPU and the need of an internal board. I don't know as much about the c128 hardware architecture as I do about the different amigas out there. But I would guess that the 1 to 2 mhz switching on 8502 and the subsequent Z80 switch for CPM would make a CPU accelerator tricky without an internal board.
The internal board the supercpu needs for a c128 is for the MMU, because the cartridge slot just gets the 64k view of memory.
However the chameleon isn't compatible with the c128 at all because of the way it does the vga output. It doesn't have to be this way, it could be made to work. They just don't want to.
http://tech.groups.yahoo.com/group/chameleon_64/message/126 The PLA problem Jens talks about is because of how they achieve dual head output (VGA+VIC), you could work round this by only supporting VGA output. At which point you don't need to write to main memory at all, so the MMU problem goes out the window. 80 column output would still work, just no VIC.
If you want a real c128 to go faster in c128 mode, then your only option is a supercpu v2 with an mmu adapter. Expensive, but it'll work.