While I like a lot of what you’ve said, and that TBC was my favorite expansion. Druids had brez and rez in TBC I believe… Classic IMO is special because of these quirks, these hard class structures. It shows contrast as to what retail has done to classes, 3-4 classes have hero and brez… 11 have silence/interupts now, everyone has a pocket heal etc.
IMO, I would have Classic+ introduce new dungeons, raids, class quest lines that would give classes and perhaps specs a way of coming forth with new gear, of course not exceeding the naxx ilvl of 89 and ultimately power creep which is the fear of many regarding Classic+
For example, T3 Dreadnaught for warrior gives taunt no chance to miss from one of its bonus’s. T3.1 from X raid could give an arms warrior a set bonus that makes MS, WW, and Auto hits a chance to hit a 2nd time for X% dmg.
Or, Paladin T3.1 gives judgement a high amount of threat like earth shock, perhaps a boomkin ring setbonus from a class questline that gives Brez no cooldown when used out of combat.