Mahout and howdah seem to me good units but not really cost-effective in terms of pop, but I want to know ur opinion.
In my opinion they should cost 4pop each after card. They are too easy to counter by numbers and dont fill the lack of artillery
Howdah is sorta ok at 5pop IMO 4pop howdah might be OP! mohout should and can be 5pop easily! 6pop is still too high! and also will make civ consistent in representing its huge population.