this looks large enough for 2 sinks.

And 10' ceilings is reasonable, it won't look odd to remove the towers.

If you like, you could have a custom mirror frame designed to take up more wall space.

I think if you have two sinks you'll need a new vanity to deal with all the pipes. I hear you about wanting to shake things up, style-wise. Do you mean full-on contemporary or change the existing style but still fit with the house? I've seen some craftsman kitchens and baths that have painted cabinets but keep a similar style, so there is some consistency. (if that's even your goal. Myself, I probably won't choose to remodel a room in a completely different architectural style from the rest of the house. But that's me)

Good point about the vanity. I guess I'll go with the trough sink, which should work with the vanity. Something like this: https://www.thebathoutlet.com/bathroom-sink-trough-ceramic-wall-mounted-or-drop-in-sink-tecla-can05011b/product/18339.

What to do above still concerns me - size of mirror, where to place lights, considering the height of the ceiling.

Interesting idea w/ the trough sink. You'll save on plumbing costs too. Your questions about the ceiling height (etc) are all valid, but unfortunately I have no suggestions. (but when I googled "bathroom with 10' ceilings," a lot of hits came up). Hopefully one of the pros will chime in. I have heard that having the bathroom lights on the side of the mirror creates more flattering lighting than the bank of lights above. BTW, I noticed the wall is painted a nice sage green. Personally I think that's a pretty color but it is a common color for craftsman style homes. Maybe repainting the walls here (and elsewhere?) will shake things up. FWIW, I know someone w/ a different style home who had wood trim around the windows but I think the walls were beige or off-white. In her case, it made the walls less of a focus, so she looked more at the trees etc outside.

LOL. These monitors, oy! ;)