The Vasari Rebel agenda is to get the races to cooperate and make a stand against their pursuers, to the extent where their tech is described as hybrid tech (their Titan has Advent antimatter generators for example.) That's why they were displayed in the intro as flying with a combined Vasari/TEC/Advent fleet.
If anything, they'll rope the TEC Loyalists and Advent Rebels into an alliance, the others are too extreme in their ways.
As for Ice, it's plot speculation, we actually have pretty much a whole thread about plot over in "I may have discovered what's chasing the Vasari", I recommend OP check it out.
