The air war over Germany was tidal, 1939 to Big Week 1944 daytime offensives by the Allies were impossible to maintain, the early Schweinfurt raids being an example. But Feb 1944 onwards the balance shifted, night raid losses increased and P47/P51 superiority reduced daytime losses.
A "what-if" scenerio is that the Western Allies put 90% available resource into building Lancasters from 1943 onwards for area attacks at night. Does this finish the German war machine? Probably. 2 x Hamburg raids every week is an enormous onslaught. But the end result is the same, Red Army tanks roll into Berlin. Is a Lanc-only bomber force a likely scenario? No (IMHO), no British politician would have removed further resource from other areas to support Harris, benefit of hindsight etc.
A Mossie-only bomber force is even more unlikely, the decision making process at the time was that bigger and more heavily armed = better. Odd thing hindsight, the American's problems at Omaha probably disappear with cab-ranked P47s overhead; likewise Arnhem, Panzers in the woods? Send in 5 Group. No more woods, no more Panzers.