I've always loved the idea of carriers, or just ships that are even LARGER than Dreadnoughts. But honestly, I don't think we'll ever see an alternative class that's larger than a Dreadnought. Dreadnoughts were / are meant to be the shining stars in the Dreadnought universe, and I feel if a larger ship existed then suddenly the Dreadnoughts wouldn't feel quite as prevalent.
If we're talking drones the ships really don't have to be very large. You could make the "Carrier" about the size of a Medium Destroyer and it's not like it'd break immersion or be unrealistic.