To me it's a question of integrity and is based on the image itself ... doesn't matter if you redo it in the future. To be honest and fair when "limiting" an edition you should make written and legal full disclosure when the image is offered as to what will be produced, and no changes after. Whether you are offering multiple sizes, each size limited to a number, or just a total printing regardless of size probably isn't as important as just doing what you say you are going to do before you sell the first print.
While certainly the concept is about artificially creating more value, to some limiting editions are effective, as they not only limit editions but also increase prices as the edition sells out. Peter Lik and Rodney Lough come to mind. I guess if you are actually "collected" and can do it, nothing wrong with it (as long as they do it fairly and honestly. I have an issue with Peter Lik because he doesn't number his prints as they are sold, but you get to "pick" your number ...and he charges premiums for some numbers. To me if it says 100/950 that not only means it's a limited edition of 950, but it's also the 100th print sold in the edition Not so with Lik - you want #777 no problem just play about $30k extra. It's usually one of the first prints made in his editions.)
For most however , (such as myself) limited editions seem to have little value.
However, that being said, I do offer much of my work as "limited" edition. The challenge is the concept of limited editions is more a part of the overall "art" market - photographers didn't invent it but have had to accept it as the way things are done in much of the art world. Many venues will not consider artists/photographers who do not offer limited editions, that's the only reason I have some of my work as limited.