I worded 1st concept weirdly... It was basically like the current repair system, broken lockpicks being repaired with duct tape. You don't combine lockpicks together. Still unrealistic though.
Ex: (Fair Lockpick + Duct Tape Piece = Perfect Lockpick)
I can't argue with the 2nd concept being unrealistic, was only thinking of game balance then. Anyway, welding machine seems like a great idea for realism, instead of having broken lockpicks repair forever-and-ever when just using duct tape.