I get that, but even I did a "big number storage" algorithm, it's doesn't take more than a week to code for a single programmer. Then implementing it properly also wouldn't take much time either. I don't know, how the current system works, but if you ask me I wouldn't start creating an idle game without creating the fundamental "big number storage" class, which for me can store up to 6 billion character long floating number. And even more can be achieved. Implementing binary summation, subtraction, multiplication is trivial and if implemented properly almost just as fast as 1+1 even for thousand character long numbers. Division is much harder, but I don't think it is necessary to implement for an idle game.
I really hope, that this is your main priority to fix right now.