The P-47s are in a difficult place, and they have always been. They have monstrous flight performance at high altitude, with insane speed and horse power up high, yet abysmal climb rate leaving them unable to actually use it in most battles, given that they end before the Thunderbolts can get to altitude. This is ironically made WORSE by moving them down in BRs, since at lower BRs battles happen at lower altitudes and end faster, leaving the thunderbolts unable to effectively contribute to the match early on.
The solution to this is simple: give the P-47s an air spawn and a significant bump in BRs. The jump in BRs itself must be significant, basically a full 1 BR for all thunderbolts across the board. Personally I play mostly the US P-47s, so focusing on them I would imagine that the D-22 would go to 5.0, with each subsequent thunderbolt model a 0.3 BR higher, with the N-15 at 5.7 and D-28 at 6.0.
This, in my opinion, benefits everyone. The P-47s get to more effectively get to altitude, allowing them to be used in an environment where they shine best, while also facing opponents much better equipped to handle them.