Re: Generations Concept Uniforms?
As I recall, the design change was made to reinforce the difference between the tone of the different series; ie that DS9 was a "down and dirty" environment whereas TNG was clean and orderly. We saw examples of this ideology during DS9 when personnel would switch to TNG uniforms when visiting places such as SFHQ.
IMO it makes perfect sense then that the crew of the Enterprise would have had these uniforms as an option. To my mind, we simply never saw them in use until Generations because there wasn't the budget for it during TNG.
For those determined to contort yourselves into knots so as to include every minor production flub as gospel, and shoehorn it into "cannnonnnnn": STOP. I don't have all day to waste on here; I quite like enjoying real life thankyouverymuch.