if you know your body, your diet, and your training methods that work for you and are advanced and a continual learner (ie, someone who is always training year after year after year and targeting weaknesses and dieting 365 days a year), then genetic potential is attainable naturally. it takes a very, very long time to accomplish this and a ton of dedication.
now add in during all of these years moderate aas with gh, insulin, t3 mixed in, then i do believe that attaining a pro level physique is very possible. BUT, that does not mean these people can step on stage and compete with the real deals. this means you can attain a crazy physique.
i believe its possible. in my case i believe it would be possible no doubt! BUT i find it pointless to use all the gear if its not a priority (i dont compete - but have been training for nearly 18 years). 1 cycle a year is good for me. but i do agree with milos, the physique is possible if you know EVERYTHING about your body and then add in the aas.