Anything you do with the blue wizards, Harad, etc is going to hit the Rings of Power problem but even worse; there's simply no source material to pull from. For the blue wizards I think there's almost literally zero, they exist, they went east, they did some unspecified but not successful stuff. IIRC that's all there is to go on.

Now look at the roughly 30 hours of filmed Tolkien in the 21st century, and ask yourself, just how good is the stuff the screenwriters made up and stuck in? It's generally pretty bad in my view, and the further from the source it meanders, the worse it gets. Any blue wizards stuff is going to be more or less right off the edge of the map, my prior guess is that it would suck, and I'm willing to use a pretty strong prior here*.

And the only reason to do any project like this is to keep shoveling out brand content to make the shareholders happy, artistically it's pretty much a dead end. It isn't going to be the story of "what really happened" because the Middle Earth canon is JRR Tolkien's work (edited by Christopher Tolkien) and anybody writing now is just a schmuck hired by the schmucks who leased the rights from the wreckage of a badly run European holding company that failed to sell itself to the Saudis. It's fan fiction, but deprived of the organic community driven natural selection of actual fan fiction.

Unless one owns a weird amount of stock in Warner Brothers, it's OK for Tolkien not to be pimped out once a financial year to keep the earnings calls sunny. The books endure, the Jackson movies are good, and in 10 or 20 years they can remake them for streaming and the five arthouse theaters still open and that's fine. Not everything needs to be an eternally expanding franchise - I'd argue very few things should be. Maybe nothing.

*
This is not a blanket condemnation of adaptations changing, adding, or removing things. In general I'm 100% fine with that, textual purity is a silly and reactionary hill I have zero interest in dying on.

However, Tolkien is I think an unusually challenging body of work to adapt. A lot of this is because the author's worldview is extremely distinct, and being the product of a fairly singular mind working on its own for years, is worked deeply into the text and narrative structure. This makes adding to it quite difficult, as any new material needs to not only make narrative sense, but not feel jarring or out of step with that worldview. This is true of any new material being backfilled into existing text, but Middle Earth is an extremely non-modern body of work. Like, even for when it was written it's very backwards facing, and the oldest parts date back about a century now. Its worldview is the late 19th/early 20th centuries and their attendant catastrophes filtered through the poetry and literature of 9th century northern Europe. I don't think that's a head space one can really get into in AD 2024.

But unlike something like Arthurian mythology, there's both a single set of canon texts, and those texts are extremely accessible to the modern audience; LoTR is not a hard read, it isn't like cracking open The Knight of the Cart. Modernizing and adapting it is simply not necessary. And because it's still caught up in our dumbass IP law, it cannot be modernized in the way Arthuriana has been, by continuous addition and audience selection over long periods of time.

All of which is to say, by all means, change and add stuff when adapting. Also Middle Earth is very hard to change or add things to successfully, most attempts are going to badly fail. Maybe dont try.