Wofano Wotanto
Hero
I've deliberately done that sort of thing with various editions of D&D. The balance in the TSR editions is already so wonky it just means you can use some tougher foes than you would normally. WotC editions are a little more tightly designed and you have to be careful about unintended knock-on effects but it's still doable IME.The one that come tommind though is from a very early campaign I ran - one of the first if not THE first - back in 1995 or so; this would be AD&D 2nd Edition. The party came acoss a cache of elven weapons, and I decided that it made sense for elven weapons to have grown more powerful over time. And that's how a party of low level characters ended up with swords and axes and whatnot randing from +3 to +6 in enchantment, plus armor and various other miscellaneous magicks.
A neat complication is to have the super-items degrade as they're used, and add a gameplay loop where the PCs can charge them back up by questing to specific magical sites or slaying unique foes.