That's why I came to m43 a few years ago... I had APS gear with large lenses (17-55 f/2.8), I used it less and less, with less and less pleasure.I think the worst part of my first foray into FF was the heavy gear and large lenses, I found myself leaving my camera at home or in my hotel room at times because my gear was too heavy (this almost never happened with M43)
And that makes me stay away from large bodies & lenses (like the G9, the 12-100 f/4, or even then f/1.2 trilogy).
However, from time to time I'm still tempted by 24x36 and maybe I'll try it one day (as a second system)... but even primes are too big... I still have to find out something (in 24x36) that really suits my needs.
The E-M5 mk3 clearly corresponds to what I want to have for my main camera... it's not perfect, there will be probably some customization limitations that will irritate me from time to time, but the basically, the ergonomics are very good and the performance/size ratio is also great.