in terms of replaceing the se/30's 8 ram slot with 72pin simms, its certainly doable, however while I haven't looked at the differences its likely some addition logic (like a PAL/GAL etc) would be needed to deal with stuff like RAS/CAS etc..
No additional logic needed if one sticks to certain 72 pin SIMMs. Specifically, one could only use Single-Banked 72-pin SIMMs. Almost all 32 MB 72 pin SIMMs (which is a fairly common size) are 2-bank. They're actually built out of two banks of 16 MB.
If you rewired the SE/30 to use 72 pin SIMMs, and then installed a normal pair of 32MB SIMMs, the SE/30 would only see 16MB on each SIMM.
For 128 MB, a pair of 64 MB SIMMs would work fine. Those are almost always single banked, although there have been a few two-bank ones.