I've recently tried to have USMC on blue and opfor, and it didn't work, at least not scripted.
What you *can* do is place the force recon units, then group them with an opfor commander (usually I use a colonel) in the editor. Then, make the opfor commander's probability of presence 0. Basically, they are grouped with a commander who won't exist in the map. You can then script, or in the init, set the leader of the group to the FR guy you want (or let the AI sort it out).
I guess you could script the groups to have an opfor colonel as commander, then delete the colonel unit... but I've not tried that one.
No clue on the changing weps pre-mission.