Prosthetic limitations of all on 4?

A few months back I encountered a patient in the public clinics who had had an all on 4 prosthesis placed in the maxilla and mandible a few months prior. Personally, I felt as though he was an incredibly highly strung person and at the state at which I met him I would be hesitant to do any large scale dentistry on. His personality may have been a true reflection of himself or it may have had something to do with the state he was in about his all on 4 treatment. The patient had gone through a few sets of full dentures over quite a number of years and actually didn't mind the dentures too much but his story was that he had come into some money and felt as though he wanted to make some positive changes to his health and transition to a fixed prosthesis. He spent the money he had on this treatment but had recently fallen on harder times due to the pandemic. 

The patient percieved nothing but problems from the treatment and reported he had chronic sinusitis since the treatment and believes that the implants had caused a nasal septal deviation as his CBCT prior to the treatment didn't report any deviation and the CBCT after mentioned bowing of the septum. I have little to no experience with implant and all on 4 so had nothing to comment on the matter. The next thing he mentioned was interesting though. He said that he felt the teeth were much too far back and his lip was sunken back. This was in comparison to the dentures he had previously and he was sure to bring in both pairs and show me the difference. Looking at this as a novice, I am wondering if this is a common issue with implant retained fixed prostheses as they derive support solely from the implants. To prevent any large cantilevers, especially in a high force patient such as this highly strung gentleman probably was, they would be looking to set the teeth not too much further forward than the implants. The issue with doing this on a previously edentulous patient is that the buccal bone would have resorbed back on the maxilla in a classic resorption pattern and the implants would be placed quite far lingually, mostly in palatal bone. As a result, most implant retained, full arch fixed bridges would probably suffer from this prosthetic limitation. It is the balance between stress mitigation and aesthetic design. Hopefully I will have some exposure to this area of dentistry in the future to learn more about the problems and solutions involved.