We do have both
They have exp requirements drastically reduced for every expansion starting with BC and the warband bonus is no more aggressive than exp gains were for heirlooms when they first came out.
Which version? because there a huge difference between vanilla, BC, WOTLK, Cata. The leveling experience has been evolving since the first expansion release.
Many people don’t want that
Random drops mattered more in older versions of the game because the quest rewards were so poorly designed.
What does this add to the game? That a person has to return to an NPC to get their new spells every couple of levels. What does that add to the game?
By making the game more boring and tedious?
Yes, you have no idea how to accomplish what you’re describing because your describing feelings not aspects of game design.