If you're in erk1024's (enviable) position and have three systems, I'd agree - save your big pro tele zoom for the DSLR system. Undoubtedly, the Fuji X cameras, like all other mirrorless cameras, are best used with a small lens. They'll handle better and will be easier to carry around.
However, if you're like me and only use one system that you want to be as versatile as possible, the size of a tele zoom isn't a problem. At the end of the day, both the 55-200 and the 50-140 dwarf any of the fuji bodies. I decided that if I was going to put the 55-200 on my x-e1, the extra size of the 50-140 was irrelevant. The 55-200 is pretty long when extended anyway.
A comment on the variable aperture of the 55-200 when using flash: when I take photo's with off-camera flash, I'm always in the mid apertures to control the flash exposure. Perhaps people do use flash with the lens wide open - it's certainly a skill I haven't mastered. I imagine it's very difficult (ND filter?). So for me, this wouldn't be an issue.
