You can swap them freely but they still may have specific properties (repair state, special bonuses, ...). At least I prepared them for that. Not sure whether I let the game actually roll those properties already...
If you dig for the parts list (I used SaveEditor Online) you can find the item codes to add things to the bot lab. If you use SEO, search for GAME > sbPartsData > and that will list the code to use for each part type.
For example, GAME.lab.parts.append(GAME.sbPartsData["SBPShell3TypeX"].clone()) will give you a basic Galaxina Shell. Nimhe still can't learn it, but you can then build your own Galaxina bot for shits and giggles.