I have a Borg scenario which works for three players. I'll check the points and get back to you. I don't think putting a 100 point fleet together too won't hurt in case the other games are really short.
Borg: 80 points to spend on 1 Borg Tactical Cube and I must have the Self Destruct Sequence upgrade.
Federation Alliance: 100 points to spend on 1 Federation ship and one other ship. The Federation Ship must have at least one crew upgrade. It's up to you guys if you split it 50/50. More crew on the Federation ship is potentially beneficial given that you will need to beam them aboard my ship.
Given that my ship appears to be just cannon fodder, I'd probably do 60-40, with you taking the 60. If we're on the same side can the cards I have that give advantages to ships within range 1-2 have an effect on your ship?