Old Kirk could have appeared during the mind meld in the first movie. It would have been brief but memorable.
i was expecting Picard to be in that scene first time i saw it
as for shatner i was half expecting something to be revealed when Kirk and Spock beamed over to the Narada (where they were basically going into the ‘Prime Universe’ and messing about with Next Generation/Prime stuff) - maybe when nuKirk is searching for Pike he sees a holo image of TWOK Shat Kirk on neros computer consol (Nero checking up on his adversary/brushing up on starfleet history from Spocks ship like in ‘Countdown‘– who Kirk is/what his thinking is like etc. it would’ve vaguely tied in with Kirk saying earlier that Nero would know what they were up to as they were part of his history so lets be unpredictable )
just a throwaway thing – kirk would catch a fleeting glimpse of his alternate future before he gets his ass kicked