Okay, so I'm not a professional or anything, so keep that in mind, in case I make an idiot of myself, lol.

What do you think of matching framed mirrors over the sinks, and then a second set of matching framed mirrors (different than the first set, but coordinating with them) for the makeup area? The pattern along the wall, from left to right, would be A-B-B-A. My first thought would be visually heavier mirrors for "A," and visually lighter/softer mirrors for "B."

I'd keep the light fixtures all the same, for continuity, either by using pendants or (like you mentioned) 3-lights on the short walls and 5- or 7-lights on the long wall, from the same line.

Am I crazy??? lol

Edited to add:

So, I'm lying there, nursing the baby, and this voice inside (that sounds a lot like my husband) is telling me that my idea here is totally Classic ODD -- Unnecessarily complicating things. :-/ I think I'd pick 4 identical mirrors, and place 4 identical 3-light fixtures over them. Do you think you'd have weird strips of wall between some mirrors, with that arrangement?

For a pre-sale remodel, I'd buy something off the shelf, three of the same size, in a very neutral, blah design. Same with the lighting. You can get fixtures off the shelf at the big box store for $50 or less that will work fine. I would not spend a lot when you're just doing it for resale. Unless it's really bad (really), you're not likely to recoup what you spend unless there are other unique variables about your house that we don't know.

Edited to add: If the black fixtures are more expensive, I would not use those either. I personally do not like black or dark bronze fixtures. It probably wouldn't be a deal-breaker for me if I liked everything else about a house, but I much prefer a chrome or brushed nickel.