Wedding traditions are more variable than ever. If it’s your wedding you have a lot of flexibility; if you and your partner like an idea there is no reason not to consider it, though budgets are always a factor. But even if traditions are not compulsory all the elements of the wedding must fit together. I mean, you can have any theme you like, but you must stay within the theme, and will have trouble if you mix different themes together. As with anything creative, there must be some coherence in what you do.
Older traditions had several bridesmaids in identical dresses. The individual bridesmaids still looked different, but at the same time they matched. Obviously the dress sizes will vary, but is you have them all made by the same dressmaker the cost might be quite reasonable.
Variations on this tradition include the same style of dress in several different colours. This can provide the best in similarity and contrast. The bridesmaids can still all look like part of a group, and the individuals can still have a colour that matches their completion.
A different variation has identical material (or at least identical colour) all used to make various styles of bridesmaid dress. Again, the small group can have similarity and contrast, while still looking like members of a group.
If your bridesmaids look like they belong together, if they look like they are all part of the same wedding, then the design(s) are doing something right. If you are happy with the look of the bridesmaids, and are reasonably satisfied that the photos of the wedding won’t look too dated when you reach middle age, then do what suit the theme and style of your wedding and reception.