Thanks you for your great feedback. I plan to later add function to reset mech construction so you can change added parts if you want to. As you said it would be too annoying to deal with some missclicks or user errors .
Also Iam sorry I forgot to add it to text window in the beginning to inform about it. But new parts can be bought in computer that is on the desk where customers comes to (with E-key) There you can also upgrade tier of usable parts and repay debt so you can "win" game.