When a new technology is introduced and there is no room to improve, it is best to downgrade the unit and the technology returns it to how it was before.
We must downgrade the Kushite archer then upgraded by a tech.
With that change. I know how angry they are going to be with that change.
The downgrade thing is good to introduce new technologies and leave the units in their current state after going through technology.
For example, you say and it seems correct to me that the units have a lot of LoS.
The best thing would be to add one or 2 technologies (even more) to improve the LoS, but first the LOS would have to be reduced and then increased with new technologies to the current state.
How much is the current LoS?
How much is the actual kushite archer firing rating?