I noticed it is very constraining to keep British fighters in range of a berlin grab without using a US carrier buy in Norway. Assuming you have Norway and a decent sized Atlantic fleet, could British bombers instead of fighters be the play?
If you had around 4 bombers, you could threaten berlin from pretty much everywhere (gibraltar [ab], london, moscow, trans jordan/egypt [ab]) while also bombing German factories when it makes sense. With 4 UK transports in range, at any given moment the Germans have to be ready for a US can opener, along with a 4 infantry, 4 artillery, and 4 bomber hit on berlin at a minimum if no other British fighters are in range.
In order for the Germans to defend that with decent odds (lets say more than 80% success), they need 17 infantry (51 IPCs).
That’s just another territory Germany needs to hold on top of Western Germany, France, southern Italy, northern Italy and whatnot that comes at a relatively small cost to the British.
A counter argument to this would be that the British fighters are necessary to lock down US landings and keep carriers full, but I think that the extra territory for the Germans to defend is worth more to the allies.