I love this theory; very, very well thought out. But as others have written, it's just a theory, not what Shatner or the franchise intended/presented.
Maybe someone could do a re-edit as an Inception style dream reality movie:
-open the movie with the rock climb/campfire and put the Sybok opening and various other scenes AFTER Kirk beds down...
-insert a brief scene of Kirk staring at one of those blue unicorns with a curious expression....
-include some Inception style "BRRRRAAAWWWs!!" on the score at various points
-let Shatner have his devil/rockmen end in CGI (see GalaxyQuest/Hulk 2003/Noah)
I kinda like the "STV as Kirk's dying thoughts on Veridian III" aspect though. Play this out and you get TVH followed immediately by TUC, then GEN, then TFF as the true, if surreal, goodbye from the original cast. Not sure how I feel about this.
yes thatd be cool (besides VI feels more of a sequel to IV than V does)