Not quite the same thing, but along similar lines... There's a process known as "banding" which basically involves cutting a wheel in half between the rims, adding a band of material and then welding it all back together to make a wheel wider. It's been a while since I've come across it but IIRC:
1) you can't legally buy or fabricate banded wheels in the UK, but some european countries still allow them.
2) you can legally use banded wheels sourced from mainland europe in the UK.
Generally only done with steel wheels though. And personally, I think it's a bit barmy.