Never had much of an issue with the size or the angle of a Glock grip.. the angle is just a few degrees more of a 1911, I mean they are fairly close.. as far as width/thickness, most double stack highcaps have a thick grip, this is something I havent noticed either.....but try finding a pistol grip larger than a Desert Eagle. After firing that, the Glock doesn't feel like it's there. My Glock grip is pretty close if not, identical to my S&W Sigma, between these two I do not notice any difference, they are that close in angle and thickness.
There are horrible grip designs, C96 Broomhandle, Dresye, on and on... mostly older turn of the century handguns where the grips are almost straight and way too narrow.. but in most of todays modern designs, most big name manufactures use grip angles that are all within a few degrees of each other. If one were to look, you will see a majority of hand gun grips pretty much fall somewhere between the John Browning design and Georg Luger's design. These are the two guys, who after even a 100yrs, out of everything else, no one has challenged the grip angle design, because it works.
Now...the adjustable back straps.. that's something I'd like to try..but.. I have a Gen 3, and looking at a Gen 2. So...I'm back stepping.