Drop the armament, focus on streamlining and top speed, like a big Mosquito or Lancastrian with bombs. The benefits are speed and reduced cost and manpower. Effective as a night bomber or death trap?
I think it would have been more effective. Especially taking into account the roughly 2000 lb in weight that can now go toward the bombload/fuel. Possibly hundreds of pounds more still, considering the fuel gains due to less drag.
Bomber Command showed very noticeable reductions in percentage losses when a) a new type or b) a modified existing type entered service with higher cruising speeds. These were generally in the order of 10-20 mph 'leaps' (granted, 1000 to 3000 ft gain in cruising altitude occurred in these cases as well).
Overall the question comes down to: would a Lancaster that cruises 60-70 mph faster evade more interceptions than the turret Lancaster would defend against.
My gut says yes. Two caveats though.
- LW night fighter tactics and mindset would probably change when there is nothing to fear from the bomber. As soon as a LW pilot has eyes on the unarmed Lancaster -- aside from losing contact there is nothing preventing him from fixing himself to his target and not letting go. This was absolutely not the case with the threat of Lancasters spitting 75-100 rounds per second back at him (at close range). How many crews were saved just by this deterrence alone -- combat not even having to take place. Anecdotes and PoW/postwar testimony indicates a significant number.
- What effect does this have on bomber crew psychology. I have a feeling you can show young airmen all the spreadsheets you want, having no way to fight back would have a tough effect on morale. The Mosquito trades defensive armament for near immunity. The Lancaster would trade it for a few percentage points in a favourable direction.
Of course the powers-that-be thought of this as well. Front and mid-upper turrets were at times removed, and ideas were put forward for removing rear turrets and replacing them with simple clear-vision stations with a pair of hand-held guns.
I can't remember if the reason this was decided against was ever explicitly stated, but Bomber Command always kept daylight bombing in the back of their minds. Evolving their bomber force away from turrets would render Bomber Command's fleet unable to venture out in daylight. Based on all the documents / correspondence I've read I believe this is what forestalled these ideas.