As an adult I still would like a great and accurate Phantom movie, but I definetly think there's an ugly white savior trope problem.
While in Iron Fist's case I'm of the opinion it is more of a soft subversion of the trope, with him being the outsider in both worlds, the Phantom would just be insulting nowadays being a "pure" white man after twenty and counting generations outside of Europe.
He would come across as anti-miscegenation (not like that's a thing anyway, scientifically).
I say set it in the 15th century or ditch the exotic history...
Better yet, go non-caucasian with the casting.
I'll defer to someone more expert in the Phantom lore, (where are you Goshdarn Batman?
) as to how important the specifics of that are to the lore, but seems easy enough to work around, or better, to expand on.
The specific location of the original fictitious island of the Skull cave where the first ancestor of the Phantom washed ashore, were never essential. Falk himself moved it from somewhere in Asia (Indian ocean) to off of Africa. Heck the fact that it can't be located and there are legends about it, should play into the whole mystery of it.
Have another legend that places it at a fictitious extension off the Hebrides, the Azores or another off Scandinavian islands in the northern seas. The inhabitants, could be long gone, which you don't even have to see can feature Celtic, Gaelic, Scandinavian, Norse symbols and look. It doesn't mater. You just need a skull symbolism theme he can pick up, and a cool looking cave, which can be found anywhere.
Ancient shipping lanes, are found across the globe, where piracy and smuggling could take place, that is what maters, that the legend and fear of the Ghost who Walks is kept alive, first among the pirates, then smugglers, to any modern corrupt global enterprise, however they want to play it.
The Phantom's suit is just one of many issues this has going against it. These properties have already had their heyday. Maybe it's just best to leave them in the past?
Batman's suit was pretty much the exact thing with a cape and ears added, illustrated with blue highlights.
If Batman can be updated, with keeping the spirit of the original, so can Phantom.
Again this speaks to going GRAY
(with only a hint of purple) with the costume...
The Black Panther's suit as above, is a clear example what they can do with modern materials, just open up the cowl.
They are hardly passed their heyday, as both have movies coming.
As indicated the original Phantom suit was gray, they just need to de-saturate the suit colors some (Spider-Man Superman).
As far as time period; both Captain America and Wonder Woman delivered successful movies set in 1918-1940s
Depending on how it's approached, none of those are necessarily the absolute obstacles you say they are.
The Phantom can successfully set up the legacy aspect, from the first to a modern day incarnation.
rest in peace.
