Surely if you were going to this much trouble, you wouldn't just reproduce a standard VW 1600 case, which is still pretty easy to locate and has a number of limitations. Surely you would make improvements.
Why not do this CAD thing for a VW CT-engine (1979-82)? This was the 1600cc engine fitted to T3 Transporters in Europe. Unlike the Type 4-based 2000cc engine that we are familiar with, the CT was based on a Type 1 engine. It had hydraulic valves, and a built-in oil filter mount in the left case half. But it apparently had some oil supply limitations, one reason why production ended after only 3 years. But if you combined the hydraulic valves and oil filter designs with a normal 1600 case, you would have the start of a 'super' 1600 case.
http://www.type2.com/library/engineg/boxeng.htm
Or even better - what about drawing up an aircooled version of the 2.1-litre Wasserboxer case, the way it has been modified by Unwin and Shimo before?