Just to be clear, I'm not saying every vex needs to speak, but they need a spokesman who can clearly state their goals, origin, and ideology. Just like what Eramis, Mithrax, Varicks, Spider, and Eido did for the fallen or like what Ghaul, Caiatl, and Calus did for the cabal, or like what Savathun and oryx did for the hive. The vex just need 1 or 2 characters who can act as a spokesperson. Sure there was harpy captain Jacob and harpy Asher, but neither really went into detail like the other species. The Geth from Mass Effect are a great example. In ME1 they were sentient machines that served as cannon fodder. In ME2 they gained a voice and we learned there was more to them. In ME3 they became allies. The vex are not that different from the geth. We know from lore they have factions which don't always agree. So it would be very easy for 1 faction of the vex to want to work with us and serve the light. Imagine a season in which an outcast mind, whose been locked away because of its beliefs, uses Praedyth to reach out to us and get us to help it. At the end of the season we free the mind and as a reward it frees Praedyth. This mind then serves as an avatar for its vex faction and takes up residence in the tower. This would make some interesting drama plot points in the future with Osiris, Saint, Elsie brey, and Mithrax.