Mercenaries
 

Unguilded folks who will sell their raid presence for plat/a particular item if it drops.

Could it factor in to the raid scene? Need an extra cleric? Enchanter? Tank?

http://www.frogtownproductions.com/b...ess_Cat3-8.jpg

highly highly doubt it. There's already an overabundance of people on raids that get nothing and still fight over a slot.

Although we always have a slowdown in the summer, what then? What if a small guild was due to take out a target but doesn't have the raid force at 12pm EST when it pops?

Could anyone from another guild come to their aid?

That's up to the individual guilds. I'm sure there are tons of people who would be happy to fill the spots, but I dunno if they'd get paid to do so.