TMP was a soft restart to the series- not a re-imagining as JJ put his version.
That's true -- but TNG, as Roddenberry saw it, was somewhere in between. Later producers married the TNG era more tightly to TOS/TAS continuity, but if Roddenberry had stayed in charge, it probably would've continued to disregard or diverge from TOS canon. And if, somehow, he were alive and fit today and asked to reinvent the original series with new actors and a new continuity, I really don't think he'd have a problem with that.
I think that as a rule, the creator of a given fictional universe will be less reluctant to see it changed or reimagined than its fans will. After all, the fans look back on the shows and movies they love and don't want to change a thing -- but when creators look back on our older creations, all we see are the flaws and the things we think we could do better now.
Maybe he would have- or just created a new batch of characters in the same period- who knows? Changes would have been there without doubt. Continuity- maybe- maybe not. Again- who knows?
I don't disagree with creators of artistic works seeing ways to improve or add on to things as times and technologies change, but don't you find it interesting that it's more typical of a writer to make changes to past works (eg add things like King), while visual artists who use static mediums like paintings, while typically never satisfied, rarely will go back and change something? That and painters are finicky... I'm not saying that is an absolute, but it just seems to be more prominant.
Is it just easier as a writer to make those changes, or is there that thing in your head that is never truly happy with something? And I don't mean that as a negative, or an attack to writers. It's just more of an observation and a thought.
On the other hand, maybe it's the medium that makes it easier.