Why would there be new models for Dilgar War era ?
Based of the rather extensive AoG books on the subject we'd have
Nova, Hyperion, Avenger, Olympus.
Based of the service dates in Book 2 add the Artemis and Oracle (probably some others but i don't fiddle around with patrol level stuff.)
All it would require would be less advanced stats for the ships, though to be honest most of the differences that are mentioned by AoG (sensors communications, targeting, power supply) are a little beyond to scope of ACtA. But anything other than the awful Hyperion assault would be a start.
Aside from that rules for the Starfury Nova(less potent stated version of the Aurora) and the Tiger (probably faster than the nova but with less guns, crap in a dog fight, but carrying missiles.) And all we need then are the Dilgar themselves and some League to get stomped on.