Just want to say I had some spare time the past few nights and threw together something that debits the vehicle costs of upgrades to the users wallet. Currently I’m assuming it will allow them to still purchase upgrades once they are at 0 as I haven’t put any logic in to stop that. Just something to say it was unsuccessful.
https://bitbucket.org/JinkLeft/vrp-ls-customs/src
I basically just tried to fork the copy of the OP’s but he didn’t open it for forking. So I just made another repo I plan on finishing up the logic possibly this weekend but you’re more than welcome to work on it yourself if you’d like.