But, my primary reason, is lighting large groups! I might get a next shoe mount flash (as a backup), probably from metz or quantum, but I doubt I'll buy the current crop of Sony flashes as they just don't seem to work very well (based on my experience with the 42 and stuff I've read online).
If you're going to use Alpha as your professional set up, you're going to need f58s, there is really no getting around it, why wouldn't you want the most versatile, compatible, and powerful hot shoe flash for you system? I don't get it. Shooting off camera is simply not an option during 99% of ceremonies, sometimes even receptions.
You're going to have occasional bad experiences with EVERYTHING, however the fact is, the f58 is the best flash for your system, period, and particularly in event and wedding shooting, you will NEED, not 1 but 2 of them, and maybe 3 if you feel it's necessary. It's a simple business investment.
Also as regard HSS, I don't know what you mean by loss of power, just learn to shoot bare and learn how to control light (which is much more important than simply diffusing it). Check out Ed Pingol's work for illustrations on what I'm talking about.
As regards light modifiers as a "requirement", it's about controlling light, not covering it. Learn manual flash like the back of your hand.
Like I said, the ABs are great, but I don't know why you'd get them before you had even a decent hot shoe flash to work with in wedding photography. But then again, obviously there are no rules.