At any rate, I don't think DLC equipment should be from other games, since online play is the main draw of Brink,
What's wrong with DLC gear from other games? Not only did they do it with pre-order bonuses (remember, ZeniMax owns Bethesda and they bought id Software, thus explaining why Doom and Fallout stuff are already in Brink, but also, the fact that online play is the main draw of Brink doesn't mean we can't have certain gear as DLC. DLC can be played anywhere, just as the pre-order gear can and the normally available stuff can.
and defantly not Killzone/Halo since neither one had Bethesda or the creators of Brink on staff (to the best of my knowledge.) Remember- the Armor DLC between Mass Effect, Dead Space, and Dragon Age are all done mostly because EA owns the lot of 'em. You'll run into liscencing issues if you throw those two games in.
Bethesda/Splash would get permission for the Halo and Killzone stuff, you know. You think Netherealm Studios just added Kratos from God of War into their Mortal Kombat reboot without asking Sony first? Yes, of course permissions would have to be obtained, that's how it works. The fact that Bethesda would have to ask Microsoft and 343 Industries to add Halo equipment into the 360 Brink and Sony to add Helghast armor into the PS3 Brink should have went without saying.
Tecmo asked Bungie (who then-made Halo) if they could add a Spartan into their Dead or Alive 4, and in return Bungie added Hayabusa armor and katana (based on Ryu Hayabusa from Tecmo's Ninja Gaiden) into Halo 3. Also, Konami and Sega both gave Nintendo permission to add Solid Snake and Sonic the Hedgehog as playable characters in Super Smash Bros. Brawl. It's an uncommon, but not unheard off situation when stuff from one company crosses over into another company's game.