I have modified a Vasudan ship and made the GVXF Hadar. It generates no power, which means your subsystems won't repair (unless a support ship fixes them) so your subsystems really do effect the way you play. Plus it doesn't recharge your shields, so I bumped the shields up to around 2000. Also, it doesn't recharge your weapon energy, so I created the Voodoo Cannon, which has it's own power source and doesn't drain your ships reactor, but is still powerful.
That might sounds pretty ordinary, but once in-game, it works really well. Sometimes you'll have to put in sexps (eg. if your comm gets down to 20%, you can't properly make communications, which FS2 doesn't automatically do 'I think').
I like the way the shields don't recharge. It gives you more of a challenge. Oh yeah, it will take a beating for a while with 2000pt shields, but they don't recharge and if your shields are down and you have a missile locked on your sorry *** , you're in trouble. I've given the example to a few people, and they like this method better than the original.
The fic:
Basically the GTVA engineers have decided that ship systems need to be regulated in a different way. Removing the energy required for recharging everything and reallocating it to other areas like your engines, etc. The ship would have a smaller reactor, so you can expect to have a larger missile compliment.
To add some variety to the game, I was thinking of giving this technique to all Vasudan fighters/bombers...
Let the critics begin.