An independent kingdom, yes, not a sovereign state in its own right. As in, High Rock is recognised as a state, and within it are numerous Kingdoms. Other states, at different times, have operated on a similar basis. Such as the Colovian states of Cyrodill. Orinism was just one of these kingdoms. And, yes, it was recognised as such.
Orinism worked fine, it was just picked on my all the other states because they didn't like Orcs having there own kingdoms and being powerful. There's a lot of stories about the "terrible green orcs" which I think is a lot of propaganda against the "savages". Orinism isn't going to help the empire, since they hardly are friends of them. The orcs are very neutral IN the elves vs humans fight. Like the Argonians and, in some aspects, Bretons. In fact, aren't orcs actually elves? Its just my feeling that they will stay out of another great war. Like they did with the first one. Because, either way, they are gaining little or nothing. Black Marsh did not rise as an independent political entity by fighting for what it believed in - it waited for a chance, struck hard and fast and ceded from the empire. The war with Morrowind would of never of happened had the nation not been weakened by the red year.
In terms of power, I would say High rock ranks in as pretty weak. Because it is not, as such, a united entity. It isn't like Skyrim or Cyrodill. High rock has a very complex political layout, which has hindered its prosperity and possibilities for millennia. When another war happens, Its my guess some kingdoms will throw there lot in with the empire, some wont.
The way I see it, Black Marsh is by far the strongest power on the political board now. Im amazed the dominion/empire are not doing more to get them on side - it would be a deciding factor of the conflict. The dominion, even if they took over Cyrodill, wouldn't invade black marsh. It would be a disaster. Evidence from numerous invasions have shown that occupation of black marsh doesn't work. This is its most powerful defence.
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In terms of the question, you wont get any solid proof either way on which way high rock is going, because there is none. Only time will tell. As I have said, I estimate the country will be split in terms of who sides with who, and who remains neutral.