it might be possible, definitly try it as TEC vs Vasari because TEC econ and production is very good, while Vasari econ and production is kinda poor. like a debate im having in another thread: Vasari have very high mobility with the ships they have, while TEC just build more ships very quickly and cheaply.
then, if you really want to ally them all against you and lock teams, set their behaviour to either fortifier or econ... maybe research, but i have a feeling they'll just tech up quickly and still swarm you.
also, try a multi-star map, so you can start up without the threat of seige frigs crawling up your a$$ in the first 20 mins, or even a galaxy-forge map where you can customise it and, if you just want the win on a technicality. give each of them 10 or so planets, give yourself like 30, make it easy to fortify, and when youve built up a big enough fleet, go for it.
im not sure if you can/will win, but those steps should allow you to at least hold your ground until you decide to attack.
but i can definitly tell you you wont do it with one fleet or even in one sitting, its gonna take ALOT of time