My Ollie's problems were found at 6 months old when he was going to be neutered, same signs you say there stinky breath, infection ect. Ollie was also a sickly kitten, I actually think he had cat flu as a kitten
I would suggest if the vets think its anything other than an infection for them to do a biopsy when he's out getting neutered, easiest way of finding out what the cause is and could also mean he could be getting the right treatment straight away, instead of what my first vets done and didn't treat the condition he actually had accordingly! Which obviously made Ollie worse
If it's found at the biopsy that he has actually got some kind of stomotitus, then the best thing to do to deley the process would be to take all of the teeth out to slow it down and stop it getting worse.
Ollie has done much better without his teeth, first he had his back teeth removed and still had the problems severly, once he had the remaining teeth removed he is doing much better but still has the problems- then again I think this has been due to not recieving the correct treatment from the start.
So Im afraid your friends vet is right and Im glad they are willing to act straight away by saying they will remove the teeth, instead of trying loads of different treatments which could only prolong and make his condition worse.
Also if the vet has already recognised the condition then the insurers will see this as an existing condition and it wont be covered, neither will anything else in relation to the condition ie- my Ollie has been on steriods for a long time and if his kidneys failed the insurance would say this has been down to the steriod over use from his already existing condition, as we all know using steriods for a long time is not good for the kidneys, so I think they would lay the blame to this.
Hope it's not what the vets thinking and it can be cleared with a course of anti-biotics