The Pancake is kind of a niche lens that I never really "got". While it has good performance I'd rather do without the size/weight savings to amp it up a notch. A lot of people really love theirs however, and more power to them.

So since you're covered on support, lighting etc., if I were choosing between a 35/2 and the 24-70/4 I'd personally go with the latter. The fast lens with IS is nice, but having 24 would give you back a bit of wide angle from losing the Tokina, and decent macro capabilities is icing on the cake. I guess it boils down to how fast do you need first? I can certainly say that once you're FF F4 on something like a 6D is suddenly a pretty darned fast lens. Both of these lenses would be great in your kit. But I'd think that the 24-70/4 + your 70-200/4 = killer combination.

Selling your 18-135 and Tokina should easily get you over the hump to a purchase. My 2¢!