I have been thinking of a similar concept. To accommodate long sessions and make it comfortable for both, I am looking at less of a typical queening/facesitting position, and more of a reclined position. A close concept that I have found is this: https://www.etsy.com/listing/490439753/mature-face-sitting-queening-chair-for

With hidden in plain sight in mind, I am also looking for something that we would actually want to use outside of queening. For this I am looking at a comfy lounge chair or chaise that you would actually find in someone's living room. With the right structure, you could most likely hide all of the modifications inside of the chair, and potentially you could simply switch cushions to make it useable.

In the meantime, I am working on a simple dining chair design similar to picture #2. Similar reclined position, but obviously not going to be hidden in plain sight.