I know the base ability isn't strong, but imho that's okay because the overall power level of the civ still increased. And antiquity age is rather early for the Khmer anyway, so I think having them be more of a late bloomer makes sense.

I think the problem with the Egyptian abilities is that they only affect rural tiles, which doesn't fit the Pyramids' redesign.

Love this mod, thanks for moving it over here - was the only one I still had from civfanatics. Only downside is the '+1 food on floodplains' you start with now is a little underwhelming, but still miles better than basegame.
Have you thought about making similar tweak to Egypt, where they can carry their production on Navigable Rivers forward into future eras? The current Egypt traditions baffle me, especially since they don't even scale per age! Even in crazy Songhai games I struggle to justify giving '+1 food on Navigable Rivers' a slot.
Maybe other D-listers like Persia would benefit from a similar mixup too. Having the '-1 maintenance on all units' civic as their tradition would benefit you more than carrying forward buffs exclusive to Infantry, since you're going to swap to Cav next era. That plus a buff to Pairidaezas (+1 gold for every connected settlement?) and I think Persia might actually be worth picking (especially after their nerf with the Gate of all Nations change...)