Thanks for the replies.
To summarize I suppose there are two issues making this a little difficult for time lapse: 1) as you say, lenses with electronic information will cause my D5100 to insist on f22 on the barrel but 2) even if the lens doesn`t have electronic information, like my e-series 50mm, I still have to uncouple the lens from the body to prevent the lens opening to openmost aperture for ease of viewing. Yes, I can wedge bits of paper here and there but it`s not a very flexible solution. I may go shopping after all...