Well, first of all you should know, that we DON'T use ships, that are invented by people, who are not in the team. Means, such fan-fic ships like the Achilles will never be in the mod.
Apart from that, it all depends on how useful a new Tauri ship would be in relation to the gameplay. Currently, and that's why there are no uberships for the Tauri, all needed ship classes are already covered by the 2 known Tauri ships and the 3 different Asgard ships.
I really can understand people who want to see more Tauri ship classes, but we simply don't need them.
And we just don't have the manpower to make unnecessary things.
But I am only talking about the first release. As we plan to release several addons for Pegasus Chronicles (which would contain new units, buidlinds, GC maps, skrimish maps and so on), it is not excluded at all that we will make a new Tauri ship for one of these addons.