Is it possible to run a game of all three Legacies vs. Iron Legacy?
Are there any special rules for having three copies of the same hero deck in play?
I've played that game. It's really hard. None of them have any ongoing destruction. The only rule that we played with, which should be relatively obvious but is still worth stating, is that any hero card that says "Legacy" only refers to that particular Legacy, not all of them.
It's not strictly speaking legal, and it's certainly not balanced. But you're hardly the first to come up with the idea.
Technically, the rules don't support playing more than one instance of a hero deck.
Not that it hasn't stopped us from doing it. 
Here’s some thoughts we mulled over a while ago. Feel free to do with it as you will!
(And my apologies - the conversation was from on the original forum site, so some of the formatting is messed up.)
Several times on G+ we've talked about an Expat-only game. This was before the Dark Watch promo, but it'd still be interesting now I think.
Why Expat exactly? Is the idea for her to represent a squad of generic gun-toting soldiers or something?
Why not Expat?
Why not any other hero who (as of the time of this original plan) didn't have multiple versions?
Shotgun Expatriette, Rifle Expatriette, Machine Gun Expatriette, Dual Pistol Expatriette, and Ammo Supplying Expatriette. Sounded funny enough to want to try it out.
For the unload shenanigans.
Alright, So Expat may now use 14 powers. . .
And playing ammo on guns owned by other players just sounds hilarious!