In short, I like to play Brink with my friend, but he is a [censored] host.

I'm a good host, but he can't join me when I am on my low level operative character, despite me putting the setting on my rank and higher.
Anyone know what to do?

Tell him to make another character i guess, one of the most annoying things is this game is the stupid rank restrictions(especially if your just playing co-op and not Mp).

When your host starts the game, have him:
hit ctrl+alt+`
si_maxRank 4

Now you'll be able to ignore rank restrictions.

Little problem there, I'm not on PC.

And I'd like him to keep his character he is playing, he already has

On Xbox you have the higher character start the game and then join in. At least that is what my friend and I do.