I have a semi hollow on order, but my "body" of experience is largely with solid bodies. My experience with perceived acoustic volume is that thinner bodies can often sound "louder" strummed than thicker bodied guitars. I can't really say how this translates to actual output amplified all things being equal. I also agree that body thickness is an important factor in overall tone, but IME probably not as much as the neck joint. e.g. SC vs DC....I prefer DC almost always, but other people sound amazing through sc guitars, just not me or I haven't found the right one. It is very interesting how differently all of us could potentially perceive the attributes of a single instrument in our hands respectively which just goes to show how much is in the "hands". I believe the in hands thing has in many ways nothing to do with the talent of the individual, but more how well the particular instrument and the individual holding it match up. We have likely all had the experience of hearing a friend sound amazing through a guitar we thought was a dog. Interesting stuff to me.
It's true, we are all going to relate to guitars differently for the reasons you say...the hands. Well, also, how our brains perceive what the hands do, and so on. I always say that playing an instrument is a feedback loop - brain to hands, hands to instrument, instrument to ears, then to brain again, adjust hands, etc.
Since we all have different brains, different hands, and different tastes, well, we're going to like different guitars.
No doubt there are thinner bodies that sound louder strummed than thicker ones, and vice-versa. I've had both. And of course you're right, the amp factors into the equation, as does the hardware, the electronics, etc. It's a system. One nice thing about being a string player is how much we, the players, influence the tone. I also play piano, and while touch is extremely important, the hands don't come into play in terms of the tone generated from the instrument, aside from our touch, how hard we strike the key, etc. Piano is like using a pick, but the "fretting hand" is a system of felt-covered hammers striking the strings. So it's less "personal."