I don't know much about that mmu and fpu stuff, but what i see for sure is that they are no other options for a plain Amiga 500 to get that amount of upgrades and features for the price point the vampire 2 offers.
For example when i purchased it theres no networking.
But now i got the sdnet support on the core 2.5, the module for cost 5 USD that kind of upgrades are quite nice and even unsuspected for me.
I don't have see much products that offer this kind of flexibility that you can just do a download an upgrade your hardware.
Thanks to the vampire i could get back on the Amiga, apart from using an emulator that was i was doing before.