I gig on both guitar and bass, and the one thing with which I have yet to go lightweight is my valve guitar combo. It's a stupendously loud 15W 1x12, but still fairly heavy, especially in its flight case (which doubles as a stand).
I would have to be seriously convinced to go down the Class D route for guitar. Matrix Amplification do a Marshall-stylee hybrid head (see pic below), and lightweight Neo-loaded cabs, but I am waiting for them to bring out a head based on a Deluxe Reverb or an AC30!