Well, the familiar is intelligent. And if you can somehow grant it access to the appropriate feat, I'd have no problem with it. The argument of it not working on intelligent mounts doesn't work because the Paladin's mount is quite intelligent.
The argument of "...some skills may remain beyond the familiar’s ability to use." still holds water though. Of course this still remains open to how the DM and the player view mounted combat working. I can't really visualize it, but maybe someone else can. I also agree with Primitive screwhead. If the familiar is actually riding you with its ride skill, you better be moving where it wants you to go. Not just where you might want to move to.