Manual reloads would be a nice addition either way. As far as having to push a button to reload, if you ARE doing that, it couldn't be the light key. Its like with the pressing a button to reload each shotgun shell, you have to take your hand off the mouse in the middle of a bad situation so you can jam a button until everything is full again. Now if say, you made it by pressing R, that would be alot better seeing as it IS the default reload key of every shooter ever. And it's very close to the movment keys, so your hands don't have to move more than they would playing with the default addons.
Well, it just depends on how you set your controls. If you do it the "smart" way, you won't have problems with building/fighting. If you do it wrong, your always have to move your hands alot when building and you will have problems with fighting.
And we already talked about reloading one round per keystroke for certain weapons like shotguns and the Milkor MGL. Didn't we came to the conclusion that it's not a very good idea? :P