Most elves should be dark haired imho, with very few exceptions...
True, but Thingol's extended family being various shades of grey/silver/golden/blonde is understandable too.
Still Elrond is explicitly dark-haired and this is important beyond just "random elvishness" - it signifies his connection back to Melian and Luthien - even if he happens to be also the only elvish descendant of Thingol currently left alive in ME.
So is Celebrimbor's being the heir of dark-haired Feanor - resembling him also in appearance - and being the "pure Noldo" - lacking any blood connection to the Sindar and their ruling house at all - a connection that e.g. Galadriel has - both by blood and by marriage, (and that even Gil-Galad has - by his Sinda mother).
All this demarcation gets completely confused by making Elrond and Celebrimbor blonde for no reason at all. It will also make Celeborn and Celebrimbor even harder to keep apart - whenever Celeborn will be shown (as I really hope they do not make
him dark-haired).
I can care less for Gil-Galad's hair in the series - even if I do like Tolkien's "all-silverly" Gil-Galad - as this is purely aesthetics and has no real bearing for the story. But for Elrond and Celebrimbor it imho has.
The weapons are less my things of concern, as fashion can change significantly from season to season.
Messing up the Numenoreans? - Less so, was never a fan of those really - beyond Elros himself - would have liked to have known who his wife was and how he has chosen her - growing up among elves all of his life before.
That would be a story I would have cared about - the remnants of the Edain gathering around a former elfing and starting something new and big on a foreign island and him learning how to be a human, king and husband. The traumatized refugees coming together, forced to re-invent themselves without the shadow of war that has defined them for generations untill now - the outburst of post-war creativity and industry and inventiveness - just to find themselves questioned by their own spoiled children who do not know any adversity and take every bliss for granted and find their "old folk" coarse, funny and ridiculous in their concerns...