That's greatest misuse of "center of gravity" that I've ever seen. Center of gravity is something 180° different that what's meant here. It has nothing to do with weak spots at all. Ridiculous idea.

And the critical vulnerability of guerillas is definately the support of their base - a certain share of the population.

Identifying will as critical vulnerability is nonsense. No being or force ever does anything intentionally without will. Saying that they stop acting if they lost the will to do so is trivial and completely useless as analysis.

By the way - Lettow-Vorbeck's force was not really a guerilla force. It was something in between guerillas and Xenophon's ten thousand.