So I've done "A Chance Arrangement" and I'm heading towards the Ragged Flagon to meet up with Brynjolf. However on my way in there are about 3 named characters who attack me on sight. Is there any way to avoid this combat, and if not, would killing these characters complicate matters further down the road?
Thanks,

I doubt you can avoid them. They are in very narrow halls. and you probably can't sneak past them. And in another quest, you'll have to fight your way out of there. If you don't kill those "bandits with names" now, you'll have to face them every time you enter.

Yeah, you pretty much have to fight them. Killing them doesn't harm any quests or anything

Yeah, they have names, but are just "bandits", no harm in killing them. You'll end up doing it eventually.

They are avoidable even at a very low level

Sprint past the first two in the hallway, drop down in front the raised bridge and keep running into the next chamber and lock yourself in the back room and hide til they go away.

Leave the room, turn right through the oil puddle staying hidden and there'll be an unarmed guy with brawling gloves in a right room full of bear traps. Fire an arrow into the previous chamber so he goes investigate (Alternatively, lure him to the oil puddle and knock the oil lamp off it's mount so it ignites the oil and burns him alive). Quickly run through the gate at the far side of the bear trap chamber. Pass through the chamber with the axe block and you'll come into a chamber with a criminal scum dude having a drink/cheese nibble. hug the wall to the right going behind the cart (remove your armour to stay stealthy if you have to), and you can reach the stairs undetected even though you might not think you can.

Go down the stairwell and you're in the flagon,

You can also avoid the brawler in the bear trap room by picking the gate beneath the raised bridge. That way you only have to kill those first two named bandits and the lowlife in the kitchen.