You may know my now that in 8.6 the US Artillery Line will receive two new arty pieces, the M44 and the M53/M55. So the M40/M43 goes to tier 8 and the T92 goes to tier 10. This creates a very messed up chronological development which makes absolutely no historical sense at all. Both the M44 and M53/M55 both lead to tanks that were out of production(M40)/cancelled(T92) before the M44 and M53/M55 were even reached the wooden mock-up stage. Even The_Chieftain is confused by Minsk's decision, he has implied they have pretty much ignored his suggestions on US arty.
It wouldn't be hard to fix this mess at all. The US designed plenty of artillery during WW2. The T16/T64 can be added at a tier 5 bumping the M41, M12, and M40/M43 up an extra tier. This leaves only one spot at tier 9 left for the T84. There shouldn't be much rebalancing needed.
The T16/T64 were two SPGs based on components on the M5 Stuart in 1943. A 115 mm and a 155 mm guns would be available for the T16/T64. The T64 eventually lead directly to the M41 SPG.
This isn't the first time WG has messed up the progression of American arty either. The M37 before the M7 Priest makes no sense, the M37 was designed to be the replacement for the M7. It would be really easy in my opinion to just swap these two since they share practically the same weapon and the M37 has more speed.
There is even more artillery that can be added to fatten the US arty line, such as the T1 Cunningham 75 mm SPG and the Christie SPGs. However they are not needed at the moment and I am feeling rather lazy.
Now what would happen to the M44 and the M53/M55? Well why not create a second line of similar vehicles such as the M52, T147, TS-13, M108/M109? I will save that for a later post though.
Stuart: History of the American Light Tank vol 1
Sheridan: History of the American Light Tank vol 2
Patton: History of the American Main Battle Tank vol 1
Pershing: History of the Medium Tank T20 Series