Karnak, been away from the house for the weekend, but just checked.
The only US fighters that do not carry a 250lb or smaller bomb are the: P-39D, P-39Q, P-40C, P-40E, P-40F, P-40N, P-47D-11, and the P-47M
All variants of the F4U can carry a 250lb lb bomb, as can the F6F, all P-38's, P-51's, and all P-47's save the M and D-11.
Infact, here is a list of all fighters in the game that carry 250lb or smaller bombs, and total ordnance capacity using those bombs:
A6M-2: 220lbs
A6M-5b: 220lbs
110G-2: 440lbs
190F-8: 440lbs
F4F-4: 200lbs
FM2: 200lbs
F4U-1: 250lbs
F4U-1A: 250lbs
F4U-1C: 500lbs
F4U-1D: 500lbs
F4U-4: 500lbs
La-5FN: 440lbs
La-7: 440lbs
Mosquito VI: 1000lbs
P-38G: 500lbs
P-38J: 500lbs
P-38L: 500lbs
P-47D-25: 500lbs
P-47D-40: 500lbs
P-47N: 500lbs
P-51B: 500lbs
P-51D: 500lbs
Spitfire XVI: 500lbs
Typhoon: 500lbs
Basically, using bombs alone, the Mossie is the only fighter capable of carrying 1000lbs. The USA dominates the list with 15 of 22 fighters able to carry free ordnance under your proposed restrictions. UK is second with 3 aircraft. Russia, Japan, and Germany are tied for last place with two fighters each.
And I guarantee I can pretty accurately rank which fighters will be used most often:
P-51D
P-38L
F4U-1D
P-47D-40
Mosquito VI
Typhoon
La-7
Spitfire XVI
Now think about that: Do you REALLY want to further increase the P-51D's usage even further? I mean for bombs alone, its tied for second greatest ordnance capacity. Hell, the La-7, probably the best fighter on this list, is just as viable an option for a JABO raid as the 110 is. Do you really want a horde of La-7's or Spitfire XVI's flying NOE alongside those lancaster?
Because I sure as hell don't. Just a bad idea in general.