i think being able to send diamonds to another player would be a very handy thing to be able to do, as well as sending items for diamonds and setting pet prices for diamonds.

Trade Broker, Player Trades, Currency Exchange
-We plan on completely revamping all trading features. Many new features will be added and user friendliness will greatly improve.
-Will allow for direct trading of Gold and Diamonds.

I've seen the suggestion for having pets for diamond prices before. I don't have any input on it, since its a legitimate currency to trade stuff in, but it's still possible to ask people to trade pets for diamonds directly instead of setting it up like a BIN. (And I think it can get confusing offering players different currencies to sell their pets in aha, there's already 4 different slot boxes for managing a pet's prices.)