I like F1 shaped cars too, but I think that it would be impossibile to manage two different kind of cars in the same challange (or two separate championship).
What we could think about is to allow different design philosophies with a common rule base.
Here is an example (just an example
)
A) LMPx cars: the ones that run this year, with small rules improments to improve realism and to make them more similar to real lmp1 cars
B) F1 with covered wheels cars (es. Red Bull X2014): same rules as LMPx but without one or two constraining rule (es. visibility of the front suspensions from the frontal view)
C) LMPx front engined cars: same rules as LMPx cars, but with a different engine/cockpit template
In that way we could have only one rulebook.
To balance the performance in the general chart, we should ask Machin to reduce/increase the engine power (maybe a test car would be needed, I have a clear idea about the loss of performance of a front engined car, and it would not be difficult to estimate the performance of a "B" type car). Maybe, considering "A type" as reference, "B type" should have 50cv less and "C type" 50cv more.