Duh, they should have done a Custom game and deleted the Barbarossa army and use IC days on a modern fleet and transports.
Lets face it, Germany was not going to touch British soil in the near future regardless of what they did post fall of France.
One might argue that maybe capturing the whole BEF might have caused a coup/collapse like in France,but I doubt it. The British Navy would have suicided to prevent a German landing if necessary.
You actually do not have to do a "custom game" to switch as Germany to a Med strategy in summer 1940. Keep a significant portion of your army in France to threaten an invasion along with a portion of the Luftwaffe. This ties down most of the regenerating British Army (who was badly treated in the spring 1940 in the low countries, France and the cross channel retreat) and the RAF. Use another portion of your army to over run Jugoslavia and Greece (6 months earlier than what happened in reality) with the Italians who are in the war. Send the deutsche afrika corps (plus a couple of divisions more) 6 months to early to north africa to pre-empt the Brits there and help the Italians go to Egypt and points east. Also use the Luftwaffe (part of it) plus the airborne troops to take Malta. In 1940, the Brits fighting alone did not have the air or the land units to effectively counter these efforts and the number of divisions of army plus the Luftwaffe requirements were small compared to the size of the forces needed because the Brits were still weak. While the Luftwaffe wasn't designed for controlling the sea and hadn't invested in the right weapons (air launched torpedoes and armor piercing bombs) and tactics it did well enough around Crete to drive off the RN in defeat and the Luftwaffe would/could have had numeric and technical superiority over the RAF in the Med for quite awhile. So these are the resources that would not go to Barbarossa (which wouldn't happen in 1941) with an indirect approach to destroying the British Empire. Whether giving Stalin another year to prepare would have made Barbarossa even a worse decision for the Germans is another question for another forum topic.