I've recently started shooting again. My current usage will be a mixture of business and pleasure shooting with a new 6D - purchased with the 24-105 F4 L lens.
The business end of things will be shot outdoors. Mostly fly fishing photos - with important action occurring just before and after dusk. I am fairly sure my requirements will include a mixture of moderate wide angle and short to medium telephoto shots. I'll have lots of other gear and will sometimes be hiking or rowing into remote locations - so the weight and bulk of my photo gear must be managed accordingly.
I've already been out shooting a few times for work and have come up with the following plan:
Primes for low light conditions:
35 F1.4 L - not yet purchased, but I have paid close attention to my last two shoots and this was one of my most used focal lengths. It should cover my need for a moderate wide angle and low light performance.
I figure I'll need two primes to cover the majority of my telephoto needs:
85 F1.8 - just purchased, extremely pleased with initial results of use, light and compact, fast AF, this lens splits the difference between what I believe will be my two money lenses...
135 F2 L - not yet purchased, but many of my shots were taken at full zoom with the 24-105. This lens would give me just a touch more length, wonderful bokehn, and low light performance.
Zooms for general conditions:
24-105 F4 L - I'm still not fully decided on this lens, it is possible that I'll sell it to purchase additional fast primes, but at the price offered in the kit, I couldn't turn it down and am very pleased with its performance so far.
70-200 F4 IS L - I had not considered this lens until recommended by my local dealer. It would cover the majority of my telephoto needs in normal conditions, is reasonably priced, much lighter than my current 70-200 F2.8, and has IS.
While I respect my current 70-200 F2.8, I don't really enjoy shooting with it. The idea of an even heavier lens isn't very appealing.
If weight is an issue and the action photos will be taken at dawn/dusk then I would go with a 135 + 24-105. It doesn't sound like your current 70-200 2.8 sees much use, no point getting the bigger and much heavier mk II IS version. I don't know that the 70-200 f/4 IS is going to be fast enough to get you enough light early/late in the day and despite being lighter than the 2.8 it still isn't exactly light. Might be lighter to pick up a 135 + 1.4x teleconverter if you really need 200mm-ish.
Or just bring the 24-105 and 6D to see if you really need more lenses - just give it a try. I know f/4 is too slow for my needs and doesn't provide nearly enough subject isolation for the photos I take at the distances I take them. The 35L is an excellent lens, but I don't know that it will be wide enough for your needs (I don't fly fish so have no idea what your needs exactly are other than those that you explicitly stated).
Fly fishing (for trout in moving water) used to be my main gig. If I lived near any good western (or even eastern) trout water now, I'd definitely be photographing it. I'm interested in what sort of shots you'd be wanting a 35 for - and by the way, I'd seriously investigate the new Sigma 35 f1.4 before plunking down my money for a 35L. And yeah, I'd want wider than f4 for morning and evening.
I wonder about the proposed reliance on a wide variety of primes when you only have one body, and much of what you will be doing will involve catching action with little or no warning. That strikes me as a perfect place to use zooms. I understand that a "fast zoom" is still slow, but I wonder how often you're going to be stuck with the wrong focal length and not enough time to change lenses.
To me, the 24-105 plus the 70-200 f/2.8 would seem to be pretty ideal--covering a wide range of focal lengths; a decent amount of overlap, and only two lenses. The 6D has pretty decent high-ISO capabilities....
