Don't let yourself disturb by other comments, you made the RIGHT choice. Forget about the 70-200mm f4, it's a nice lens, agreed, but it's for hobbyists and travellers. If you want to go pro, you need the f2.8 IS, period. You can afford smaller apertures on shorter lenses, or if you work on a tripod. Handheld you need 2.8 minimum on long lenses. Why do you think fashion pros go for the 200mm f2, or 300mm f2.8 ? They don't spend hard earned cash for the glory of it, it's because they NEED that extra stop for faster apertures and better background blur. In many occasions this extra stop will save your day, that's what you pay for, not for extra sharpness, contrast or whatever else. IS is helpful, but does not replace the right speed, nor the proper camera handling technique.
IMO it would make more sense to have the 50mm 1.4 and the 70-200mm 2.8 the the 50mm 1.2 and the 70-200 f4. My guess is, if you change your 70-200mm f2.8 for the f4 you will quickly regret it on one of your future assignments.
One side plus of the big lens, however stupid it might sound, is that your clients will be more impressed, since for most people pro equipment = pro photographer. People's mind is set in a way that if you show poorly dressed, come with a cheap used car, etc., you are not successful in your business, so you are not the one they should give their money to. I hate the rule, but it's how it works in a lot of businesses. So consider your new lens as an excellent business investment as well.