My question is. Am I missing anything mission critical (outside of being able to play Jol-Nar) to play a 6-8 match? Thanks for any advice/help
Well, if memory serves, each sprue in the base game has three system tiles on it, plus whatever could be squeezed in around the outside. Hopefully the sprue that has the Jol-Nar tokens on it is also the sprue that has their Home System, which means you're really only down two useable system tiles.
There are more enough other races that you can just leave aside the Jol-Nar for now. You may want to check that you're not missing the Home System for any other race, though.
If the missing sprue happened to be one with Strategy Cards, that might be a bit more of a pickle. Although the Shattered Empire expansion came with a full set of replacement SCs, so even if you are missing some of the originals you can use those ones instead (they're better anyway. =P) The Speaker token can easily be replaced by just about anything for the time being, if that happens to be missing.
Beyond that, you are at worst down a few trade goods. You should be good to go for a game with any number of players.