You could probably use the browser's localStorage to save game data, although if its stored directly as json it can be edited quite easily. Base64ing the json save would make the save harder to edit, although not by that much. You can find tutorials for localStorage using Google, and I don't think it would take longer than an afternoon to implement if the game's internal structure stores everything in one structure. (Disclaimer: I've never actually messed with localStorage, nor am I a js dev. I mostly do python but know a little javascript. I could try to help out with the game but I might not do very well :p)
Yes, that's a nice idea. I have looked into that before, and I am aware that it's easily editable. However I am not very concerned about that since cheaters can always find a way to cheat. They can even inject some JS snippets if they want to cheat.
Anyway, the concern is that the data is not centralized in any singular location, and rewriting the code will be quite time consuming. I am currently focusing on my other project so don't have much time to complete it atm. I might come back after I finish the other project (which is going to take a lot of time). There are a lot of ideas too that never got implemented, so I'd like to implement them as well when I return to work on BTC King.
Thanks a lot for your suggestion. I really appreciate it. Also, if you wish to give it a shot (I too am not a JS developer, but did come this far), I say you should go ahead and do that.