if you look at the release candidate towards the top of the page, it has a floppy only installer. FreeDOS is probably the option I'd go for, personally.
Alternatively if you want to be more period-correct (but legally questionable, which may also be period-correct depending on how disreputable one's friends were at that period, I suppose), there are loads of abandonware places that you can get MS-DOS from. If you want the eccentric option, I probably still have OpenDOS discs somewhere If the card boots OK off the FreeDOS boot disc, to the point of trying to install off the CD, probably about any DOS boot disc out there will work.
The problem with the SIMM expanders is that you're increasing the number of power-sucking chips by a quite a bit in addition to increasing electrical loads on the memory circuits. I wouldn't likely use them outside of a PC since they often have more power to spare and are more tolerant of weird memory configurations. Plus they're really tall so wouldn't fit well in a compact Mac or most of the II series or similar machines with limited RAM clearance. That said, I got a set of 72-pin SIMM-to-168-pin DIMM expanders in a box of random stuff once. Never tried to use them but they may work in old PCs that can use unbuffered EDO DRAM DIMMS.
Since some people are working on remanufacturing SE/30 boards anyway it shouldn't be too difficult to reshuffle some wires to accommodate 72-pin SIMM sockets in place of the 30s. Maybe flip the ROM SIMM 90 degrees and scooch the FPU over a little? Or maybe just use 4 72-pin sockets instead of 8 to keep things mostly in their original orientations? 4 sockets will still yield 128MB.