Firstly, JKR's impact on both the film industry in the UK, and on Universal's approach to theme parks cannot be overstated. The game was changed. It's been great for both art forms. For that, we can be thankful.
USGB deserves a fully themed, immersive land that's up to the same standards, and, by the concept art, we're missing that for now. Ordinarily, having a UK property in a UK park makes the most sense. JKR would probably even push for something on a bigger scale, or a more complete scale then we've seen before. And as others have said, I think a lack of HP would be felt, and possibly met with confusion. The Sun in particular, who reports on theme parks here more than any other newspaper seems to, would certainly run stories about it by disgruntled fans.
But I'll say it. JKR has become a very controversial figure. She's positioned herself as the figurehead of an entire movement against trans people, and whether you agree with her or not, it's not going away, and will end up being part of the conversation surrounding this park. Unfortunately, visiting a Universal Theme Park with a Harry Potter land now actively funds her political campaigns, as she's proudly stated. Maybe you're happy with that. But like the racist themes and ideas that Splash Mountain were built upon, this is a facet of theme park production and discussion that will only amplify in the next six years, whether you want it to or not. Whether you agree with it or not.
I'll be frank. I don't want it here. I don't want that conversation. Theme Parks can be the great leveller - a place we're all brought together. If you agree with her, or if you don't, maybe it's better that conversation is kept out of this park entirely.
Universal Studios has the solution and the opportunity to bring a unique land, written and "set" in the UK, to their theme parks, to the standard set back in 2010 - and that's a Lord of the Rings area. People literally fly to New Zealand for the Warner Bros Studio Tour equivalent. That's not to say that the existing HP areas should go away, because they're beautiful pieces of art created before she became so actively vocal. Leave them as they are, and add to them if you want to. But there's a chance here to do something different and more benevolent and I say - let's do that instead.