I'd rather they just fix the friend requests so refusing them actually works, and so they don't interfere with blacklisting.

Currently, even if you click "No" on a friend request, it still remains in the Pending state until you actually select and cancel it from your friend list. It should be fixed so that "No" means No. And you should be able to blacklist someone regardless of whether they've sent a Friend request. If those two things were fixed, the Friend request wouldn't help gil spammers and they'd stop using it.