Howdy folks
I am joing this discussion a little late, and I admit that I haven't read all the posts. The problem with closing with an opponent has been overlooked by most gaming systems. The suggestions I did read here are all good. What I have done with this problem is not to provide someone with a "close" weapon a bonus to hit, but giving them an AC bonus if they managed to get inside a larger weapons effective area.
So Polearm guy is attacking shortsword boy, shortsword boy deftly slips in past the effective range for the polearm. Shortsword boy gets a bonus of +2 to AC.