
i would hate to be in your position because i can't live with only 3 lenses.
as per what you wrote, it seems that you may be gunning for the 16-35L II more for a 'good to have' situation. in fact, getting a wider lens does not make sense re achieving the shallow depth of field.
perhaps an option is to get the 50L and borrow a wide angle lens when you need to.
You may be right. I want to have a wide angle to use when i need to (landscapes, travel). I think the 16-35 II may be better as a photojournalistic style wide angle lens than the 35L but i am spoiled by the sharpness of the 35L. I don't really need my wide angle to be very fast. I would just be happy if someone told me that the 16-35 II is not that bad compared to the 35L in apertures like f4, f5.6 and f8 at 35mm.