Yes, there are. I used to host By-Pass lobbies. But you would have to by pass your Ps3 to get into CL's but you can only get infections without by-passing it. But if you want to host I would by a older Ps3 then jailbreak it than buy another one. I might make a tuT on how to by pass a Ps3 with out taking down the firewall.
Yes, it is possible through PS3 Jailbreak. Mods are also available on a lot of social website like youtube, facebook, twitter etc. You can search over there.