Hello All,
I think that Matthew is thinking about the planed Invasion around June-July 1940 by German Forces to Invade England.
Their is a good book on the subject: Invasion: The Alternate History of the German Invasion of England, July 1940 by Kenneth Macksey. It is a very good what if, I have read it a number of times.
On the rules, I would only allow what forces Germany and England had at the time, ie: no Panthers, Churchill's, American forces etc.
You could also allow Ships and Aircrafts in, Thus allowing other Members to join in.
Of course, I don't know how Matthew will want to set up the rules and regs.
Just my 2 cents on the subject.
Cheers,
Bruce