I'm not sure ascenders and descenders are the only things factoring in here. I guess doing a visual blur on an image of a word could help to spot characteristics of words. Admittedly, the ascenders and descenders would have a probably primary role in aiding classifying. So maybe it's an 80%/20% thing.

At a guess words with unique clusters of vowels would also stand out say 'Hawaiian'. Or other words like 'cameraman', 'minimum', 'consciousness', 'neuroscience', that all probably have a certain shape or density, even if they are flat.

This regex dictionary may be useful: http://www.visca.com/regexdict/ /^[aeiuocmnrsvwxz]*$/