I've always allowed rogues to sneak attack if someone is in melee and they are attacking with a ranged weapon from directly across from that person. I do not aloow the +2 for flanking but my rational is that the defender cannot properly defend arrows flying into their back while trying to avoid...
If you check ouy the Cheater Book of Feats there is one called "clever monkey spins the branch" I believe it does something similarto what you want to allow. I think it's worth a feat, and still fairly better than a spiked chain in most situations.
In my world everything has max hit points. I know this may seem odd but for a long time I allowed rerolling of ones just because of the high levels of combat. See first of all I don't understand why gaining hit points is random at all, if a class learns to "roll with the punches" better than...