There's a few options that could work.
One could be as simple as a GW where you can scale the difficulty level.
Another could be an option to fight squad arena battles, but with no reward/rank change/etc
You could create enemy squads by having the ability to select any toon and change gear, mods, zetas etc.
You could battle allies and/or guildies
So many ways, and I don't see a downside (other than resources spent on it rather than elsewhere...but seriously, what are we losing there?) And some of these ideas are probably pretty simple to implement.
Need to monetize it? Can be as simple as charging a few crystals. Besides that, simply creating a better product often pays for itself. They could promote a whole new mode by just tweaking something that already exists... we know they can do that.
