Am I the only that thinks that the best future Boston backcourt is Smart and Hunter? If not, they would definitely be the most entertaining guard combo. Essentially you have a bull-in-china-shop player paired next to a crafty gazelle with range for days. Keep in mind, my optimism/excitement is based on the future, with no regard to the crowded guard situation.
Defensively: Hunter played pretty good defense from what I saw in Summer League, and anytime your 2-guard has a 6'11 wingspan, he can be effective (Remember Shaun Livingston guarding IT4?). Only thing RJ needs is to reach the 200lbs mark to prevent getting bullied by stronger guards (but that's why Marcus would provide the switch anyway). Of course, everyone knows what type of defense they'll get from Marcus.
Offensively: RJ's range and shooting would be ideal to stretch space for Marcus to drive. Unlikely pairing Marcus with a midrange shooter like Avery, putting RJ would give the shooting that matches how Pace&Space should be. Right now, I would say that they're both above average at ballhandling, with room to improve. But assuming they do, they can share ballhandling duties that compliment each other. We saw flashes from both of them that shows how well they can pass the rock, so that's another plus.
It'll be interesting to see how the analytics view this combo by year's end, but it'll be the one I look forward to seeing the most.