This seems like something that would already have been suggested if it were possible, but I couldn't find anything about it anywhere with a brief search, so here goes.
It would be great if there were a mod that allowed you to upload skins somewhere, maybe not even necessarily minecraft.net, in a 1.8.x format and have all the 3D body parts be applicable to a player running the 1.7.10 client. The reason for this being that the more detailed skins are really the only reason I personally would want to update to 1.8, however many server utilities, and even other mods, are most stable at 1.7.10.
The best way for this to work, in my opinion, is to have it work with a server-side mod/plugin so you could enter the skin into a command (in the form of a direct image link), and that image would then be saved into a file within the server associating it with that user, and that would then be translated into a skin visible to any other players on the server with the client mod installed.
A bonus feature to having the skins uploaded directly to the server in this manner, especially for Role Play servers, would be the ability to instantly change skins in-game via command, without any need to restart your Minecraft client.