The outcasts arn't really a threat they mostly just patrol the wastes around the fort and only move in somewhere when there is an extreme opurtunity like the VSS facility.

The Shi are a faction of Chinese Immagrants in Fallout 2. You have the oppurtunity to either help them grow and prosper by killing the Hubologists or die out, because of the Hubologists having you kill them... Ironically the Hubologists in all their ending die in some sore of matter. One involving a space shuttle.

As you said, they COULD have the Shi as an ally. I would more likely see them as being a supplier though who give sell them this advanced technology. For all we know the Shi could have been wiped out or will be, and absorbed by the NCR. They didn't exactly have numerical advantage to the NCR and if the BoS could be beaten, I could see the Shi being too.

Actually, they are descended from the crew of a chinese nuclear submarine that ran ashore near San Fransisco. Damn ignorants. <_<

The Shi could be allied or they could be apart of the NCR. I would like to think they are allies. I would like to think they are Allies. They supply NCR with Tech while NCR provides food, power and anything else. Way I see it, the Shi are very advanced maybe more so then the BoS and Enclave. They have some awesome fire power and they do have T-51b armour for sale. NCR would like to take control but the Shi want their own Empire. NCR is just expanding into the north. NCR ends up going to war with the BoS and the NCR can't go to war with two powerful factions. So the NCR offers an alliance. ShI being peaceful agree to it. Over time Shi prove a good ally so NCR leaves them alone.

Well since the West Coast Brotherhood cut off ties with the East Coast Brotherhood its pretty doubtful that the East Coast would know about the war between the NCR and the West Coast Brotherhood. The NCR would probably be pretty impressed with the East Coast Brotherhood Of Steel.

Well the scouts couldn't really do much but establish diplomatic channels they certainly couldn't go to war with Lyon's. So really its a silly question. The two forces are two distant to have much interaction.