Great question! And it does open up a whole bunch of complicated issues. One is the problem of re-directs. Here's a great explanation of that http://www.wikitree.com/g2g/51703/behind-merges-identifying-lowest-numbered-profile-correct
So, if you do complete a merge to "merge it away," which is perfectly acceptable, just make sure you merge into the final profile, or the lowest numbered profile (with the correct spelling of the last name at birth). Otherwise, you could create (or maybe contribute to) a re-direct.
The other is how WikiTree works, which is really by Profile IDs. So if you change the spelling of the last name at all, it wil assign a whole new ID # (thereby back-firing on any idea to simplify things). I learned this when I tried to change a name UNKNOWN into Unknown, and started a whole new profile number!
So in order to recycle a profile ID (or number), you need to use exactly the same last name. Otherwise, all data is changable. Maybe you could find a family where there were several children, but only one child has a profile already in WikiTree. That's where I might start. Maybe choose a child with a first name which is not too common (to make searching for duplicates easy). Then do a search for existing profiles, just so you make sure you don't make a duplicate.
A lot of nuances, aren't there? Not at all sure I understand all of it yet (not a programmer). It's just one of those things where I learn something new every day, and that's one of the best parts .