I would love for them to go darker with these films. They have a lot of stories to use, especially with Mighty Morphin' being 3 seasons long. You've got evil Tommy, the Island of Illusion, Rita stealing the Rangers' power, Jason being captured, the team losing their Zords, Tommy's change from green to white, and that's just off the top of my head. They could easily spread all of that over a few films!
Bulk and Skull definitely need to go though, or at least, smarten them up and not make them look ridiculous as that sort of humour doesn't translate well in big feature films with the darker storyline. Maybe they should use them as the characters that try to expose the Rangers' identities (like they already have done but failing less so epically) to increase the tension throughout the film and create smaller storylines alongside the main plot. It would emphasise more the whole 'Rangers battle to save the earth, but also battle to keep their identities secret' thing and keep with the original story.
I have been watching some of the more recent Power Rangers seasons and I quite like the Samurai and Super Megaforce ones. It was the Super Megaforce season that has got me to take a look into the Samurai one and it's not all too bad. The ones produced by Disney are utter shit though. I'm glad Saban is doing it. With the money being put into it, do you guys reckon they'll still use footage from the Super Sentai series or actually do their own stunts and use their own costumes? The only problem with recycling the Super Sentai footage was the inconsistencies. The filming and production are only just a little different, but enough to notice the switch between the two.
Speaking of villains, I do like Dayu's story from the Samurai/Super Samurai Rangers. Her storyline with Deker is really interesting and ends up quite touching, especially for a kid's TV show. It has the basis of a good young adult fiction story in there already.