That is not what I was looking for, I am not planning on modifying the BIP itself or submit a new one. Just the "implementations".
For example these are reference implementations for bech32 encoding, it lacks c#, or this has only one c# implementation and is pretty bad (IMO) because of its unnecessary complications.
So my question is if I wanted to submit my BIP39 implementation which I already have or maybe if I wanted to add the bech32 that doesn't exist, what are the things that I should consider? For example of the top of my head should it only be implementation of that particular BIP or can it be part of the bigger library having other stuff?
I assume that you would change the BIP and include links to your implementations. Anyway, if you can't get a good answer to your questions, you might contact luke-jr. He maintains the BIPs.