A decision to remove turrets may have been the correct one when viewed 70 years on, such is the benefit of hindsight, but it would have been seen as gambling with men's lives at the time. The German response to Allied successes was (generally) fairly rapid and effective where resources permitted, tactics for dealing with Window (I might have typed Windows previously, the shame) being a prime example, Tiger tank in response to Red Army T34 and KV-1 another.
The average speed and height of the RAF bomber stream over Germany certainly increased during the conflict, the average speed of German nightfighters increased by a significantly greater amount, compare RAF (night) losses with USAAF (day) over Germany in the last few months of the airwar
The balance of the airwar at night always fluctuated, even as late as Jan 1945; after Big Week it was all over for the Luftwaffe day fighters. And with hindsight(!), Bomber Command should have switched the heavies to daylight raids, leaving the Mossies to operate at night.
Certainly Tallboy was an effective weapon, but it was never going to win the war in the West in 1943/44, although effective area bombing of industrial targets might have (Speer). Alternatively, finish Berlin by Jan 1944 with a force comprising primarily of Mossies, each able to carry 8000lbs of munitions to Berlin on a dark winter's night ..
There's no doubt that Upkeep was a magnificent example of British engineering, created by a tenacious designer and delivered in perhaps the finest and most inventive feat of arms in the airwar 1939 to 1945. But it wasn't followed up, allowing the Germans to rebuild the dams (Wallis was reportedly furious), so the overall effect on German industrial production was minimised.
Re: Saumur raid: very effective use of the Tallboy, but it doesn't win the war in the West.
Re: Tirpitz, the Tallboys were again certainly effective, but against a target that no longer presented a serious threat to the Allies. The sinking freed RN assets (particularly capital ships) to prepare for service in the Far East, which - in hindsight(!) - made little difference to the outcome.
Re: Crossbow, Mossies were the most effective means of dealing with V1 launch sites.
Re: had the war gone on long enough? What-if scenarios - by definition - are opinion. Type XX1 wins the Battle of the Atlantic, Red Army rolls into Berlin? Wasserfall stops USAAF day bombing, night raids intensify, Red Army rolls into Berlin?