The STP (or A-booking to real market) had shown that quoting and execution was worse than MFF his own datafeed. So bad or unfair trading conditions from MFF side is garbage.
BUT the traders all traded on FX prop firms CFDs with over 50:1 leverage, so that is not allowed for all US residents. Here is a point from CFTC side I see.
So they will likely forbid for all US residents trading CFDs. In UK it is different trading with CFDs is allowed but in EU no more than 30:1 leverage, recently also with leverage restriction in Australia, so I expect a change here on FX prop firms, on that point.
BUT all traders did not trade any product so even NO CFDs too because it was all simulated or virtual trading. So maybe there could be also an exception even for US residents. If in fact no CFDs were REALLY traded only VIRTUAL CFDs where is the problem then ? Even for 100:1 leverage I see no problem then if all is virtual. But then STP thing is bad, because a part really hit the CFD market, which is then NOT okay. So in the end MFF would need a kind of gambling license only for taking hundreds of millions of real money. That could be all, in the best case or outcome I think.
Another problem I see in the near future on all FX prop firms, that nearly noone is getting a payout like less than 1% of all traders.
BUT there are more than 1% of all loosing traders COMPLAINING about the prop firm...
SO that can have more cases from regulators because of that imbalance between number of complaints in relation to profitable traders.