I just wanted to let everyone who's interested know that I've made a fully working backup system for the SNES. It has got 32MBit RAM, 1MBit BRAM, works with both LOROMs and HIROMs and comes with a Windows transfer utililty.
Here are some pictures:
All games which I've tried so far are working without any problems (some of them must be patched, though). Here is a list of these games:
I'll release all necessary schematics along with detailed instructions and explanations at some time.