So your taking the orcish armor into heavy, like in skyrim? I'm completely okay with that.
In skyrim I didn't feel like every race had it's own metal, more like some races were predisposed towards certain materials because they knew how to use them. Also, skyrim kinda fixed/ignored this issue by having it possible to work with one armor type until it was better that the base of a higher armor (like upgrading steel to be better than ebony) while still having ebony potentially even better. And, theoretically, you could say the orcish smithing perk is only gotten by asking to see an orcish smith and learn how or by taking orcish armor apart. (Though i'd like to have quested for that if that were the case, but it could be argued ALL armor perks are this...)
Also, orcish armor is notably a lower heavy armor in skyrim, and the real reason orcs may be known for their armor is the skill they possess in upgrading it, something that's not inherent in the ore itself, but in the crafters' skill. Since steel is more easily gotten a hold of by the empire, and smiths who work with it likely know how to make good armor using it, it could be argued that getting orichalcum as an ore is a waste in comparison to both the armor they already have rivaling and base armor they could make with orichalcum and also a waste in comparison to having smiths good at using glass and ebony which are--barring daedric and dragon (which the empire either wouldn't want or has no way of getting lots of)--the best armors of thier build.
I do think it would have been cooler if the creation of orichalcum was like the creation of steel, a mix of two ore types... but whatever. Lore in any videogame is going to be wonky if that videogame is a series and remaining current.
I do wonder if you could slip a skyrim/dragontail orc armor into the game to highlight the tribal differences... but Vvardenfell is fairly far away from them as opposed to the more mainland parts of morrowind.
Out of curiosity, what would the nomad orcish armor look like? And also, do you think you could post this armor with a greenish overcast? I'm really curious how it would look, if it really is as horrible as you say. I didn't think the armor in skyrim look that much different, so I'm curious to see what difference it makes in practice.