I have an "ignore the legend rule" tribal deck that is pretty busted. It's a bit of a glass cannon, at times, though. Still, I like the idea. Most legend rule breaks are for creatures (then again, the vast majority of legends are creatures), but there are a few ways to copy legendary artifacts even now, like
Mirror Gallery or
Mirror Box with any copy spell. It does beg the question, though, what specific legendary artifact are you trying to copy? Most that come to mind for me don't really stack anyways, so it doesn't matter. I feel like the most busted things to copy for voltron aren't even legendary. Like how just 3
Thran Power Suit gives +9/+9 and ward 6, which seems like a better deal than 3
Shadowspear. I guess an extra
Blackblade Reforged or
The Reaver Cleaver is pretty cool. A copy of
Helm of the Host seems pretty cool, but that's just copying one thing to copy something else and takes you further away from the voltron strategy as you go wider.
Anyways, if you are in Boros, run
Cadric, Soul Kindler. It gives a copy of every legendary equipment you play (and more) for just one mana. I know a lot of equipment decks are in Boros colors, so it should help out. The token dies at end of turn, but if you can copy the artifact any other way, you can keep them even if they're legendary.