I am at the moment working on a new cruiser, which is kinda what you're after. It's slightly smaller than a Fenris, packs an LRBGreen beam, two AAAf's and some Terran Turrets- although it aint finished yet, I would estimate that four of these could take out a Demon.
I also ran a test battle- but more a small ships one. A Deimos, a aeolus, a leviathon and a fenris against a Moloch, a Rakshasa, a Cain and a Lilith, each facing their counter part. Interesting thing is, 3 times out of 4, the Terrans won.
"Supernova, ya supernova, supernova goes pop
supernova, ya think it's over but the supernova don't stop" PM5K
Death:"Arnold Judas Rimmer... your life is over. You will travel with me to the-"
#knees death in the groin#
Rimmer:"Remember matey, it's only the good that die yoing"