I dont think you could fix the predator helmets, because the problem is with the entire head, the predators own forehead is not shaped correctly and thus the helmet is shaped incorrectly to match.
And i'm not saying figures have to be perfect, it's just theres certain things you wanna see done right when theres no reason they shouldn't be. THe predators head, and his mask are the most visually appealing and well known parts of the character, so to do them incorrectly is noticable. Add to the fact that its simply oversized for the body is a mistake. It's the same complaint people have for the likes of sideshow luke. That likeness is spectacular, but his expression and the size of his head compared to the body surely puts some people off, theres no real reason for it, it just is. Its an obvious mistake but its too late to fix.
THats why i'd hope for hot toys to fix the predator 2, but at this point i doubt it. In the end, alot of hte 12 figs i own are by far from perfect, but the key with them is none of them have one major obvious flaw that holds them back to the point of being noticably bad. At least not a flaw that can't be fixed. With my hot toys superman he really just needed paint on the face and bam its a perfect figure, same for medi wolverine. My sideshow star wars figures needed a touch up here or htere a costume refitting etc and bam they look perfectly good. Nothings gonna be perfect movie accurate as you say, but that doesnt mean we should ignore the obvious mistakes just cause the rest is fantastic. And thats not to say nobody should like the figure, but to deny that hte heads to big, or mishaped would be incorrect and thats all im saying.
Say you lvoe the figure as is, thats fine, just dont say its got nothing wrong with it, and im not saying you are doing that, but i was a little worried you might from your first comment, and i've seen that happen from other folks on this board about figures (like the great medi debate), a willingness to defend a flawed figure and unwillingness to admit it has mistakes because of dedication to one or other different elements.