Damn, I hate trying to throw cold water on a good imigination, but welding and honing are pretty inprecise. If you could bore the lube groove to diameter and machine the edges of the grooves, you MIGHT be able to make it work. You'd still need to be able to polish all surfaces enough to remove the machining chatter marks or your bullets will forever be sticking in the mold.
I believe anything less than this is going to result in an uneven lube groove. Even if you can get it out of the mold, it's not going to have its center of gravity along the center of axis, and depending to what degree, could be seriously inaccurate even at CAS distances.
HOWEVER at the price of a set of Lee molds, you could probably afford an extra set just for grins and giggles ta see if Ya really could make it work.