Green Lantern yes. good call. - The costume's material should be similar to Routh's costume in SR
Nightwing... acrobat, going to need a suit that allows him to move. - True but it must be spandex which looks very durable as well as flexible
Martian Manhunter. Going mostly naked is fine for Dr. Manhattan, but I want to see J'ohn wearing a bit more. - His costume was always dorky. Spandex could work but it might make the audience laugh at him even if they make a CGI/make-up which is excellent
Red Tornado. he's robot he can wear whatever he wants - not if he looks silly wearing it
Huntress do I need to elaborate? - Nah, she needs something like leather, same with Black Widow
Harley Qinn (I know she is a villain, but she is so cute) - I can this working
Aquaman swimming in armor? more like sinking - Aquaman isn't a normal person. An armor's weight could not slow him down in the water at all.
and Flash(again going to need to move) are the only other ones that come to mind at the moment. - Or they could use the fabrics Spider-man had or similar variant.
For the non spandex crew here are a few that I think could get away with it.
Azrael - Should be like a suit of armor
Mr. Terrific - possible but his costume could very easily be adapted with other materials without the risk of looking silly in live action
Lobo - not sure