Fed won his first slam at close to 22, so if Pete is 6 years older then it means he is 28, this means we are talking of 1999 Wimbledon Pete in place of Philippoussis ... Ok, Pete could best 2003 Federer, but then the next year 2004 Fed faces 2000 Pete, Fed beats him on Grass this time and also beats him in New York because Safin did beat Pete in New York in real time, if Safin can then the Federer who doubled bageled Hewitt will also do it. 2001 Pete vs 2005 Federer is even worse for Pete because he does not beat Federer anywhere now, not even in new york.
So that's it, Pete beats Federer at 1 Slam I.e 2003 Wimbledon
You have to agree that Agassi is not in this timeline as 5-6 years older because if Djokovic only had 1 ATG older to him in 6 years range then Federer should also have only Pete.
Now if you want to do the iteration with Agassi and not Pete then Agassi probably win an AO maybe, nothing else..
So that's what I meant, older ATG cannot do any real damage, taking 1 Slam from Federer is possible, not more for a 6 years older ATG, only a same aged one can do some real damage....nobody else. Also same aged ATG makes it harder for Djokodal below and so some slams below could trickle down from these guys to Fed and that ATG...