These halftracks look great, its really nice to see some finesse with wargames models.
For armoured platoon/ company sized games the 251/9 Stummel with 75mm L24 and the 251/2 with 81mm mortar would be great.
The next one on my list would be the 251/22 with PAK 40 75mm L46
As pointed out in an earlier post, parts could lead into further products, the PAK 40 AT gun for eg and the 75mm L24 would work on a 250.
A good one for late and post war, weird WW2, onwards would be the 251/22 UHU carrying the 60cm searchlight for infrared night fighting, this was also used on a ground mount alongside flak batteries throughout the war (great scenario/mission objectives)
The 251/16 with flamethrowers would be a briliant addition too.