Firstly, you'll need a module to allow ban evasion. Mods are gonna try to ban you when you use it and getting a module like this developed is essential in a game like this.
Secondly, try to keep all of your code to a singular sprite for easy updates. If poison wants to update the game and his update renders your client unusable, it makes it easy to transfer over the hacks to a newer version and fix it.
Thirdly, even if you feel your client has too many features. It doesn't. No client is ever complete as there will always be new things you can exploit.
These are just a few things I would recommend to someone wanting to make hacks for a game like this.