First the reason for the suggestion, I mix and match collection armor pieces a lot...I almost never use an entire armor set in their default configurations.
My suggestion is that unlocked collection armor pieces be individually reclaimable rather than being required to reclaim the entire armor set. It takes an inconveniently long time to drag/drop and delete all the undesired pieces once the desired look has been accomplished.
Barring a change that allows armor pieces to be reclaimed individually, flagging reclaimed collection armor pieces that are bound and unmodded as junk that can be sold to vendors for zero credits would serve as an alternative method of eliminating currently lengthy process of discarding all the undesired armor pieces. As long as the junk flag is only applies to already collected, bound, and unmodded collection items, a warning popup wouldn't even be necessary, as if it's accidentally sold, it can just be bought back or reclaimed again from collections.