With IB, Dukascopy, Baxter, LMAX, and a few others you can submit orders as often as you like, on whichever side you like, make or lose as much money as you like (subject to risk limits of course so stupidity does not impact other traders), and none of above brokers shut you down or slow you down or limit you in any way.
If you do arbitrage or your trade in and out too fast,( like in 1 minute), you will be banned by most forex brokers.They do not bet against you but they need enough time to hedge . Otherwise no problem with them no matter you win 10 times or 100 times in a month or two.
I saw lot of traders made 10 times, 20 times in a few month without problem withdrawing their profit from brokers.
FXCM case does not prove every broker does the same thing. Just like when you see a policeman do robbery does not prove every policeman does robbery.
If brokers all don't allow traders to make big money, who the hell need them? They will lost all customers and go broke fast. On forex forum, every small issue on the brokers side has been posted and traders all watch how brokers solve it. If they can't solve it fairly, there will be huge amount of their customers leaving them.
I see OP is new to trading and has many wrong understanding about trading.
Like S&P average 8% annual growth, he wants to leverage 10 times to make 80%. This will blow his account fast ,since 8% is an average growth. There are many times the index is down like 10% or 20%, then your leverage account will blow up many times.