I do still have quite a lot of WW2 Desert stuff. Last year I downsized it because 33 tank brigades were to slow to play. That was using a figure scale of 1:5ish. I've now gone 1:10 but can pretty much field 15th and 21st Panzer Divisions together now, all of 7th Armoured Division for the Brits plus a couple of infantry brigades with their support. I have no Italians.
FIW has always appealed to me. I also love GMT's Wilderness War which would be great for providing a campaign backdrop. As a campaign, you wouldn't need a lot of units, that's for sure.
Recently, I've enjoyed playing Nimitz (Sam Mustafa's WW2 naval rules) a few times so that will probably be my next diversion. I inherited the rules and a bunch of 1:6000 ships from Peter J's collection (mostly Pacific) - at least enough to make a start and they are soooo cheap to add to. Nimitz is one of those great one evening filler games - quick to set up, easy rules to learn, quick to play out a battle running up to a dozen ships a player. Very good fun. Also 1:6000 ships take up so little storage space!