The only thing Multi-Crew can do is operate turreted weapons or fly one of the fighter ships. At the very most you can have a gunner and a fighter pilot. So basically a 3 person wing. While using multicrew, you can't have other non-fighter ships in your wing. Multicrew is a wing of its own.

Multicrew introduces profit duplicated awards for bounties. They are also changing this so wings of ships will also duplicate and not split the bounties.

Multicrew players can not operate scarabs, launch 2 fighters or pilot the owners ship. However the owner can launch his npc pilot to fly a 2nd fighter.

Multicrew do not share missions, cargo profit, or anything else. Only bounties.

To answer your question about launching a fighter while landed... you can not.

If you guys are looking at doing ground bases, I can help you guys out. I have a gunship that can wreck any land high security base. Just come find me in teamspeak in the elite dangerous channel most evenings. FYI there are usually 3+ of us playing ED and in Teamspeak on a regular basis and would look forward to meeting others who are playing Elite Dangerous.