I love what they did with light Redguard style. We don't need to change much really, just add some polygons here and there and higher res textures. And I know that Redguard style looked different before of course.
"I bear the cruel weight of certainty. Total, absolute, relentless certainty. People rarely comprehend the luxury of doubt... the freedom that comes with indecision. I envy you."
―Sotha Sil
There are some really good older styles, but sadly they are just not rendered and detailed to the same high standard the more recent additions are, making it difficult or certainly frustrating to match up styles to create a good look. Consequently a lot of older styles are just not used.
If Zos are looking for some inspiration outfit system wise... they could do a lot worse than consider how Anthem has tackled some aspects of outfitting. Anthem has added the welcome ability to set the base material of any armour area, meaning all the colours render and appear the same on that same material. This would in one fell swoop remove the excruciatingly annoying ESO feature where a colour will look totally different on different armour styles, again causing huge issues with putting together an over all look.
Too be honest I actually prefer some of the older styles to some of the newer ones that have been released.
Just depends on the person, would rather they focused on more important stuff than potentially screwing up old styles and potentially screwing up people's outfit combinations.