I sometimes forget that that the DLCs weren't originally integrated in to the base game (that actually came later via the legendary and then the Special Editions).
For that I apologize.
Also, the armor being questioned is... ugly. I mean, yes it does look like something lore friendly, if we're playing Oblivion. That set does not look like it fits Skyrim aesthetics at all, I would just ignore it.
https://www.nexusmods.com/skyrimspec...tion/mods/1061 Which is just a remodel of the Imperial armor, looks lore friendly enough.
https://www.nexusmods.com/skyrimspec...tion/mods/9865 For the Heavy Armor characters out there.