I've done something similar in my Dark Nova Mod. What I did was took the expanded sizes for fighters and carriers (as well as most other too, by the way) from Andres Lescano's Ultimate Shipsizes Mod. IIRC there are 10 fighter sizes and 12 carriers. The largest fighters, Battle Squadron-2, is 60 Kt and can pack a sizable arsenal.
Also, fighters are cheaper to research than unmodded.
As for PDC, what I did was reduce the damage done slightly and decreased their range to 3. I also added a fighter weapon mount that gives +1 range (at a increase of supplies and size). This means that fighters can actually stay out of range of PDC.
With the carriers having so many new sizes and being relatively inexpensive to research, they gain the benifit of larger weapon mounts faster than other ship sizes which provides the same benifit as a warship that I think you are looking for.
In the Dark Nova games played so far, if you arn't using fighters, then you are sunk without a massive number of standard ships.
The newest mod, Dark Nova 4 is avaliable here:
http://seiv.pbw.cc/Download/filelib/1035/DN4+Mod.zip
Re: Making Carriers and Fighters more usefull.
Hybrid Mode
