Basically if you buy NTAG215 nfc tags (
https://www.amazon.ca/NTAG215-NFC-St.../dp/B071KTC2J6) you can program them (say with an Android phone) to be any given amiibo (once, you can't rewrite to them, at least not so that the Switch can read them)
And as far as I know if your island is full and you invite someone via an amiibo it just asks which one you'd like to move out (but I'm not 100% on that)