Sure, he's not the best choice for imitating Gane, on first glance, but who is? Gane is more than just the way he moves, he's also very intelligent in the choices he makes. That is definitely what he has in common with Rico, high fight IQ. A lot of people could give technical advise, but not many are as accomplished and experienced a striker as Rico (not to say Rico is the only good choice). Just an example of something you don't immediately would tell, but most likely is kind of 'hidden' knowledge that he possesses because he trained a lot with Tyson Fury, which very possibly gives him a good bit of first hand boxing knowledge he got from training with the best in the world in a different striking sport, than his own. Not to mention all the other people he got to train with since he was young, and all the styles he has seen. He's a great bet for finding some creative solutions to the problems Gane possess. Rico also has a good bit of MMA training experience, so I think he has a pretty good understanding of what works and what to look out for in MMA, Though Gane is mainly a striker, so it's not too much out of Rico's depth regardless.
Rico also has an exemplary winner's & champ mentality and experience, which is something that is always good for a fighter to be surrounded by and can very definitely raise the fighters game up.
Also, on another note, people ITT seem to disregard the possibility of Ngannou bringing in other guys (other than Rico) and possibly someone who can mimic Gane better,
But people want to act like they know exactly what is best for a fighter as soon as little details are known, even though they really don't know at least 95% of how his training camp will actually look.