This part I don't understand. This is an open source module - you can make any changes you want, these checks would run on client side anyways.
For example, you can add your own logic to disable this payment option for certain products, or disable it for payments from, IDK, first time customers... So, what's stopping you from putting an
Code:
if($_SESSION['cart']->show_total() > 5000) $this->enabled = false;
on let's say line 78...
And, as with all plugins here, you're most welcome to post your (better) solution for the community, and if anyone else decides to implement it, nobody can stop them. That's the whole idea with the community contributed plugins here...