The language will be simplified, logical, and contain no irregular verbs or similar pointless inconsistencies. Learning an alien language is hard enough as it is without having to deal with the alien equivalent of "knew, known, and knowing". It can also be valuable if a galactic empire falls. The Lingua Franca will then allow different empire fragments to communicate. Much in the same way that Latin allowed different countries to talk after the fall of the Roman empire, even though Spanish is not much like French.