i use the orbital base in the training TF, and as far i can see they never fall out of orbit.
I RP as the task group is wargaming around the planet mostly doing planetary assault/defense exercises
Awesome! That could simplify things. My carriers seem pretty fuel efficient currently task force training around, but this will save even more, plus keep them on station if they need to respond to something.
I use a carrier design with a single commercial engine for CV(T). This also is a very efficient way to deliver out of date local defense fighters to colonies with a fighter base, or current fighter to fleet carriers in another system. They are very cheap, and at ion tech have a speed of ~1000 km/sec. I would never let them near a hostile ship / system. Although they make a nice supplement to the pdf's around Earth.
Do you mean you are able to make a Carrier Classes as a Commercial Vessel, or are you using the a Commercial Engine on the Military carrier because the CV(T) is intended purely to shuttle fighters around, and that while it's incredibly slow it's also incredibly fuel efficient/long range?