The Amazonians being Kryptonian is actually a great idea. I could swear I actually suggested this on GAF at some point, but I've already bullshitted so many DC movie ideas that I don't know any more.
Part of the reason that Wonder Woman has been considered "unfilmable" is because of the Greek mythology stuff. It's hard to pull that off in modern cinema (See Clash of the Titans remake, that other movie Henry Cavill was in), and especially hard to mix with much more generally accepted characters like Batman and Superman who don't gel with Greek mythology.
This fixes everything. Cleanly. You can even have the gods exist. Zeus, Ares, Hades, and such were just their day's Superman. And it works believably with the Man of Steel universe. Fuck, they can even explain the magic truth lasso. Kryptonian interrogation technology remaining from the ship that landed on earth. It even works in feeling unique enough to differentiate it from Thor's sci-fi explanation.
Wonder Woman being weaker is... It's just weird that they would come out and say that like it's a good thing. Kind of demeaning. But, I think I get what they're saying? Kryptonians have been breeding with humans for centuries and the bloodline gets watered down eventually. Or maybe since Clark was a "natural" birth he's more powerful or something. I don't know. I can rationalize it, I guess. It's not like it would be any more interesting if she was just a female Superman minus a few superpowers. But Wonder Woman has to have something to bring to the table.
Batman is this genius and master strategist.
The Flash can essentially slow time (Going by the idea I gave earlier)
Green Lantern can materialize stuff with his mind.
Superman... is Superman.
Fuck, even Aquaman is king of the sea.
What does Wonder Woman bring if she's just "Not quite as strong as Superman." That lasso isn't gonna cut it. Warrior experience might help a little, but still... She needs something that she's the best of.
Norse mythology worked in the MCU. I see no reason why Greek mythology can't work in these films.
As for Wonder Woman, she's basically the best fighter of the whole group.