CharlieAlphaVictor

My general opinion is that trying to make one of these machines, most of which were outdated even during their time in frontline service, into an effective fighting vehicle in 1943 would be quite the uphill battle. Perhaps a tank destroyer or reconnaissance vehicle would be more plausible, but you'd have to sacrifice so much space and weight just to fit a viable gun on the thing you would have extremely little room for anything else, let alone trying to add additional armor.

I agree, I foresee a lot of knock-off Marder or Sturmgeschutz-type designs being submitted. Realistically, there's no way to increase the effectiveness of the armor on any of those designs to the point where it would actually matter. Even a British 6-pdr. would make short work of any of the listed designs. Might I suggest resetting the timeframe to immediately after the fall of France? I feel like that would put whatever monstrosities the myself and the other contestants come up with on a bit more level playing field. 

Mini-competition suggestion: fix-a-tank
 
Contestants will be given an existing, flawed AFV design (or a selection to choose from), as well as a country and a time period. They will then be asked to propose modifications, reworks, conversions or fixes to improve the design or modify it for a specific task.
 
The submission should include one or more drawings or blueprints, a description of the modified vehicle and a description of how the modifications would be accomplished.