[Other] Fixing link trades/battles in a preexisting ROM hack? (Crystal Kaizo)

Hello,

I want to learn how to fix, or find somebody (who I'd pay) that can fix the trading and battling in a pre-existing ROM hack, specifically pokemon Crystal Kaizo. I understand that this is probably a very complicated and asinine request/path to go down, but it is something I want very much. I know that other ROM hacks have fixed trading or even kept compatibility with the OG games.

All I want is the ability to trade/battle between two separate physical copies of Crystal Kaizo.

Does anybody know of any resources that deal with this topic? Or have anything to add/offer?

I greatly appreciate your time, and any help or info you might provide, thank you!

Okay, I've found out more specifically what I'm trying to ask.

How might I go about adding back in the attendants in the union room? They are missing. Keep in mind this is a binary hack.
Please explain it step-by-step, including what programs I'd have to use -- explain it as if I have severe brain problems and I am 3 years old, please.. or if you are willing to just "do it yourself", I'd be willing to compensate you for your time. Thank you.

I'm not allowed to attach pictures, or else I would, but it's just a picture showing the union room attendants are not there.