Which lens to complete the collection?

I'm putting together a set of lenses to use for travel photography with my 5d mk2, but I still feel like a tele/medium tele is missing.

My current lenses are:

- Canon 50mm 1.4 (works very well for my purposes so far)

- Voigtlander 20 mm Color Skopar (for landscape. Love the small size, and IQ is good when stopped down)

I also own a 70-200 f4 L, but I find this a little large and too conspicous with that darn white color.

So what I look for is a lens that can fill at least part of the 70-200 range for portrait and landscape use, but at an acceptable size. Lenses that I have considered are:

- Canon 100 mm 2.8 macro IS (cool with the macro possibility, but is it a good portrait lens?)

- Canon 135 mm f2 (seems like a pretty darn good lens, but is the 135mm format a bit too tight?)

Any input/ suggestions?