There’s an imperial law stating omegas can’t inherit the Crown due to a past omega who went on a rampage.
But yeah, I agree. Like if revealed he was an omega and married his boo tang, he might not be King but Queen is just as good imo lol - just might not have all the control a King has in regards to laws/ruling the kingdom. Though, they could simply push to change the law too.
Though, there’s also the aspect of elevating his maternal family by becoming Queen/being a dominant omega as well.. Politics are tricky.

very rash behaviour I know, but if they went ahead and just revealed their alliance and relationship right now I think it'd give Etienne a much better chance at the throne rather than following the empress. the king trusts them both two so really the Herace family seems to be the most butthurt on their own