I know that there was mention early on (beta time) about being able to customize sights. If this were to be included, that would be amazing. Also, I specifically have a hard time seeing the iron sights on a number of weapons (bolter, hellbore, etc.). I don’t think it would break immersion to have a small Tridium (glowing green) insert in the front sight post. This would make it much easier to align the sights.
Official response: “This isn’t CoD”
Easiest way to implement this would be through the cosmetic you can apply to your weapon. This already changes the sights with weapons where the sights are different on different variants. Example being Lucius Helbore, if you want rid of the side tails on mk3 variant, apply any of the current cosmetics available for the weapon and it will have the sights of that cosmetics instead. As long as you have that cosmetic, you can apply it to any of the variants in the weapons family. These cosmetics could include scopes or iron sights of various types without changing the functionality of the weapon or having to introduce new system or even worse, even more variants for the roulette store.
These cosmetics could and should be available through either penances or through the weapon cosmetics tab at the armoury exchange or some fancier looking ones from the weekly mission store.
Edit: One of the weapons that might require a new key to be pressed being introduced, a toggle to switch between hipfire and sights for example, is plasma gun. I would love a reflex scope on to that (and an actual stock). Or allow the primary fire to be a charge similar to Lucius Helbore and let the secondary fire be ADS instead of charge. These being split is a bit unfortunate when it could just use the same system as Lucius does.