And then what. You weapons have the same range as everyone else. Your missiles have the same range. It is the same reason why the f22 production was haulted. The air force went off how it could detect a enemy so far away. When councils asked them "can we hit them from that far" it was met with "well we need to invest in long range weapon development and research". The f22 uses the same AIM as every other jet, and if memory serves right the f16 sensor range already exceeds the AIM 120a and i think the AIM 120c also.
Then you also have the issue that the f22 and the f4u before it. Yes it can fly far and detect and shoot an enemy before the enemy can. Both these ships were ripped apart once they were in dog fighting range. The enemy simply avoided missiles and closed the gap to get the kill.
There has to be a disadvantage to the p38 to be balanced. It is bigger, has more range, is 2 person ship, has a kitchenette for long distance flying. Has more weapons. My bet is it will get hit on manuevering just like the original p38 did with rolling. I also dont remember reading anything on speed just that it goes far.