Great looking models! Not my scale, although i might be tempted by 15mm, especially that next year FOW operation barbarossa should be out
I also think that 1/56 scale might be worth it, albeit as somebody mentioned due to the cost involved it would have to be popular, mass produced types such as panzer Is, t-26 etc. Osprey is releasing set of rules soon to play SCW as well and i imagine it will produce some more interest in 28mm wargaming of that period. And obviously models can be used for early WWII plus VBCW which has actually quite a following. So I sincerely hopee you will mange to release those kits in 28mm.
And I second opinion on 15mm gun kits- good idea to release them as they are normally most expensive part.