For the record, such a change not effectively being a nerf is mostly impossible because the only reasonable damage increase (from 160 to 200) with an accompanying ROF nerf would actually increase the TTK for the most common targets (medium tanks at 640hp) even if DPM was kept the same, as the number of shots required to kill such a vehicle would remain the same because of overkill damage. It would be a good way to make the Jackson more balanced (becoming less effective against everything and becoming more specialized against heavy armor) but it definitely would be a nerf and it would require other changes for compensation.
Ah I had understood that damage/reload time would be balanced so that mediums would be 3 hit for Jacksons and increased reload time would have benefited p4s so that they could play around the longer reload time for their advantage. I think this would be a great change if they would somehow introduce the m10 as a default vehicle and put Jackson behind some extra major tier and balance that out. But without this kind of compensation I find it hard to justify why Jackson should be nerfed against medium tanks. But that being said not every faction have the same structure and some have weaknesses and strengths that are necessary for balance. Jacksons should still dominate mediums in able hands if this change would be introduced.