As far as Varis is concerned, he's already met the Warrior of Light directly and has received a considerable amount of intelligence in regards to his activities. Given that Garleans are described as focused on efficiency in the lore book and that Varis is praised as an excellent tactician I have a hard time buying that he wouldn't be open to the idea of an alliance if it meant a true, lasting peace for Garlemald and a means of successfully combating the Eikon threat upon the world stage. Yet I doubt things will be so simple, especially with Zenos, Elidibus and Asahi being caught up in it all.

Perhaps the Emperor's attempt at reaching out to the Warrior of Light is legitimate, though Asahi intends to kill Emperor Varis at the peace talks and frame it on the Warrior of Light? That would mean that Zenos would end up becoming the next Emperor which wouldn't be good for anybody. I just can't buy that Asahi cares about reform when he supports someone as unhinged as Zenos.

I think it'd be an interesting twist if Varis was temporarily overthrown, reached out to the Warrior of Light for aid along with some supporters and then opened up a route to work side by side throughout the rest of the expansion and much of 5.0 to redeem himself and reclaim his position as a reformer of Garlemald. It'd be a nice change of pace to the somewhat predictable trend of entering a new region and killing/dethroning whoever happens to be in charge. Plenty of leader figures throughout previous Final Fantasy games secured their position by the end of the game's stories, after all. Rufus Shinra is a favourite example of mine and his original attitude is very similar to Emperor Varis'.