Starmada projects, part 1: Starmada Trek
I find Starmada: the Universal Game of Starship Combat more than suitable for sci-fi gaming. It's quick, easy, has a decent ship construction system, and can easily be modified for specific settings. Here's my list of ongoing conversion projects. For most of these I have many or all of the ships I need done, I just need to sit down and crank out some scenarios.

Starmada Trek - original series style Star Trek. I'm interested in two periods here, both inspired by old FASA products. The main one is the Four Years War. Under the FASA timeline this was a Klingon/Federation war fought just prior to the events of the original series. IIRC Kirk was a junior officer during the war. I feel confident I could get ten or fifteen scenarios out of this project. After all, who doesn't like a good Fed/Klingon shoot-em-up? And it helps that I have a metric assload of ship designs available and already converted.

A smaller cource of inspiration would be the Unknown War, a.k.a. the Demon War. This war precedes the Four Year War and is fought by the Klingons on their front opposite "known space" where the Feds, Romulans, etc. reside. Starfleet calls this action the Unknown War because they can deduce the Klingons were busy on another front, but have no direct knowledge of the situation. To the Klingons these events are the Demon War, a crusade to push back an agressive monstrous race called the Kinshaya (Klingonish for "demons"). Little is known about the Kinshaya, save that they look like demons from Klingon myth and attack with utter ruthlessness. The one illo I have seen of them looks like a cross between Swamp Thing and a balrog. So anyway, the Klingons fought a desparate holding action against these guys, who attacked with no apparent provocation. The Demon War is one of those great "no diplomacy is possible because the enemy are such freaks" type war. The Kinshaya flit about in giant spheres with warp nacelles. As far as I can tell no stats have ever been published for their ships, leaving the field wide open for interesting designs.