Indeed, a fusion engine would be ideal for unlimited loitering and range. I was, however, trying to maintain a symmetry with the other drones. They are all Tech Level D with either a fuel cell or ICE engine.
I did upgrade the drone carrier tank in another post, and it does have a fusion engine;
http://bg.battletech.com/forums/index.php/topic,11628.0.htmlI would love to see a fusion VTOL statted up, if you'd like to give it a shot and post it.
I also have the VTOL mini painted now, here are some group shots with the other drones and the carrier.