Ew
pls no let him run it seems obvious that he doesn't even know Java.
(Quite literally the easiest language to learn imo)
I would suggest re-making the cache aswell, completely dumping all the data into a readable format then re-creating the cache to make it less likely to have shit stolen, have a better understanding of the cache since well, you'll have the developer that created it, also can do as you said and can add shops and etc.. (Also, no .config files all over the source pls, all stored in cache and dynamically loaded pls (70% sure that is what his source is full of)