Yeah, that sounds like a pain.
Also, what do you mean by unlocking all of the available LBX parts? Because, unlike weapons, there is a limit to the number of parts you are allowed to carry. People aren't sure yet whether it's 216 of each type (head, leg, etc) or just 1000 total but either way it is not enough to carry 1 of every kind like the weapon code does.
Hmm, unless the limit increases later in the game (my save is still pretty early on), it seems to be a natural limit of 111 items per LBX part category; excluding head which seems to be 112.
Which is a good point-- I won't be able to have them all in my inventory at the same time.
Perhaps what I should be pursuing is a way to make them appear for sale in the stores.