Probably not possible at all anymore. I'm surprised this was even possible at one point. I'm sure you could still modify your name on the client side, but chances are the game relies on the server to provide the names of the players in the game, so modifying it on the client side, would not change the name everyone else in the game sees.
That being said, to modify it on the client side, you would just need to attach to the process and scan the memory for the string (your username). If it helps with your search, the username string is probably UTF-8 encoded (they now allow special characters outside of the range of ASCII, so they must be using UTF-8 or higher).
As for your specific issues with using MHS, I have no clue how to help you. I do not use MHS, nor have I even heard of MHS before.