Coins in market

The only potential for abuse with this one is new account creation. If Haypi could lock down the account creation to 1 account per device, this would not really be an issue for abuse.

They would also need to exclude this option from PVP because it WOULD get abused there.

It is locked down, well execpt for jailbroken devices But there are other ways to get new accounts legally

Yes,
There are ways to get new accounts legally, but you'd still have to put the coins up on the market and hope that no one else snatches them, similar to the way treasure is swapped now...