I'd only use 2.8 @ 16MM for shots of the Milky way which aren't something I dabble in all of time. My plans for 16-20mm is for certain landscapes, city shots (mostly f/8-16).

Right now, I only use the 35 for photos of my daughter inside which have worked out really well, primarily @ 1.4 and 2.8. I could use the 35 for group shots but is a bit too wide for my style.

I had thought about the 24-70 lens but I have the 24-105II and I use that for my landscapes, not for portraits. I would only use the 24-70 from 50-70mm so it would not be worth my investment at this time as I'd rather have a 50 and 85 with lower apertures.

I just feel like the 35II is not going to be utilized that much and condensing 2 lenses into one would be good. My biggest concern is the 16-35III's corner quality. The 10-22 was awful in the corners.