what counts is if it works.
So it doesn't really matter about the POV, it's if the novel holds together as a complete and satisfying story.
QFT.
If you're drawn to multiple first, I'd say go for it. It's hard, but I love doing it, and I'm not the only writer of historical novels who's found success going this route. Check out Michelle Lovric on Google - she has five successful historical novels behind her already, and her new one 'The Book of Human Skin' (which comes out with Bloomsbury in April) is going to make her a big, big name. That's multiple 1st too, and is possibly the best historical novel I've ever read. (God, I hate her)
OK, neither she nor I (and I'm a lot lower down the food-chain, having only a deal so far and no evidence to provide in terms of sales) fit the very different US market in historical fiction, which seems to be far more female and romance skewed and is seen as a kind of 'genre'. In the UK, historical fiction is mainstream and huge, and if you can tell a damn good story in a way that makes people care that's all that matters. For what's marketable over there, you're better off listening to US members.
All I can say is that it's a pity market has to dictate your choice. I write multiple 1st because the voices in my head are all different, all disagreeing with each other, all fallible, all having something to contribute no-one else can, and I can't bring myself to gag any of them. The
only significant character to whom I don't give a voice is my MC. No man exists as he believes he does. I want my readers to make up their own minds about this man by seeing him three dimensionally - through the eyes of his servant, his antagonist, his political opposite, the woman who loves him, the man who hates him.
I know who he is, but who am I to tell anyone else what to think? Let them read the evidence of the witnesses who knew him, and decide for themselves.
Louise, who probably needs to see a psychiatrist.
PS - Gratuitous advice warning - Ophelia, it's probably a typo, but your OP uses a phrase that is death to any query or submission, which is 'fiction novel'. A novel is fiction by definition, and the use of that phrase has been quoted many times here as the quickest ticket to the wastepaper basket there is. I'm sure you know that perfectly well; you probably started to write 'historical fiction' and changed it to 'historical novel' without deleting the 'fictional' bit. I do that kind of stuff all the time...