Perhaps the most simple and easy way to increase the perception of mouthfeel is to decrease carbonation. Glycerol seems to play a big part as well.
I get the opposite perception from what you describe. Less carbonation perceives as less body, less mouthfeel. Still samples of beer always seem watery to me for average strength brews.
However, as you state, increased glycerol production does equate to increased mouthfeel to me, as well as increased foam production and stability.