The idea of jamming these new FPGA boards into the older legacy Miggy cases is very appealing, and likely the better solution in the long run. Chasing down custom chips isn't terribly difficult if you went the "recreation board" route, but there is still a limited supply of them, even if they won't become scarce anytime soon.
I'm looking very forward to an FPGA solution with Ethernet. I'm not an Amiga gamer in the least, so the stuff like the minimig never appealed to me at all. I'd LOVE to have a more modern daily driver FPGA Amiaga with networking onboard to run my BBS off of.