What stops the Tempest and 262 from rendering everything else useless applies here.
There're many facets of fighter capabilities. Speed, armament, durability, maneuverability, range... through an entire spectrum of speeds altitudes and situations. Beside speed and maybe range the 262 is among the worst in the game in all of those categories, including armament when you consider the battery of MK 108's effectiveness in a dogfight.
The Tempest is quite a good, well balanced aircraft, maneuverable, durable, great guns fast... short range maybe...
The thing is, that with fighters you need to engage the enemy... in any situation where you're killing you're vulnerable to be killed.
Bombers are a completely different ball game... speed, defensive firepower, range, durability and payload are the only things that matter. The B29 would be the best in the game at
all of those categories by a significant margin.
Also bombers do not have to make themselves vulnerable to drop their ordinance, beside a 1-2 mph loss from the bomb bay doors opening....