Again, it's impossible to come up with a system that is unexploitable but to use it an excuse to simply not even try to improve the current situation is BS. Yes, changing the system so that gym fees can only be changed on Friday would still allow a very small, inactive group of players to be exploited for a small amount of money. Now contrast that to the current system where 100% of the games player base is vulnerable to being ripped off for huge sums by shady gym owners.
I'd also like to know on average how many gym members managers haven't logged in the last seven days and their average bank balance. I really doubt it's anywhere near 20 per gym and most of them probably have less than $500 in the bank.
I might be coming off as a dick here but I've been screwed a couple times now and I know of at least one other gym that tripled their rate right before fees were due with no warning to anyone. Having a fighter be forced into full time work because of a scummy owner is ridiculous.