Guppy, you have mentioned before your opinions that the C was the most important model. But which C?
The vanilla early war C? The field-modified C that is essentially the pattern for the later J?
I would say there is definitely a need for the J, even if only to fill in for the later field-modded Cs with waist and tail guns added in. I know we have the strafers, and I'm happy for that, but I think there is as much a need for the B-25J as there is for the Bf109G-2.
If you look at the MTO C/D Models, the ETO RAF birds, the CBI birds, Aluetians and the early PTO birds, the glass nose version is the most representative without the tail gun. In terms of the 5th AF birds the C Strafers are the most important. Just looking through the 345th BG History, not all of their strafers had tail guns. It was not standard practice
Also keep in mind the J models didn't show up in the PTO with the 5th until the late Fall of 1944. They flew their C/D Strafers into 45. The RAF did the same and when they got their first J models they were not popular with the crews as they were heavier and seemed more sluggish at the controls.
Photo below is a 2 Group RAF Mitchell II late Fall 44. No tail gun to be seen. The RAF even got some later model Mitchell IIs with the tail gun position with the rear dorsal turret. There was no provision for guns in that tail turret however.

1943 B25D in the MTO. Again no tail guns. If you want I can post photos from 44 showing the same. Again, it's not like it didn't happen, it just wasn't standard practice.

Again I'm not against the J but it would be down the priority list for me. The C/D's did all the heavy lifting with the J showing up late. I really believe HTC gave us the best compromise for both MA use and for Scenario use. The J just wasn't the player the early birds were.