What if.....Denethor survived

[Tuor of Gondolin]

I found this topic debated in another forum, and I have mused on it myself.
What if Minas Tirith and Denethor survived.
Two quotes
1) from LOTR
"I say to thee, Gandalf Mithrandir, i will not be thy tool! I am Steward of the House of Anarion. I will not step down to be the dotard chamberlain of an upstart. Even were his claim proved to me, still he comes but of the line of Isildur. I will not bow to such a one, last of a ragged house long bereft of lordship and dignity."
2) In Letters(#183) "Denethor was tainted with mere politics: hence his failure, and his mistrust of Faramir. It had become his prime motive to preserve the polity of Gondor.....Denethor despised lesser men, and one may be sure did not distinguish between orcs and the allies of Mordor. If he had survived as victor, even without use of the Ring, he would have taken a long stride towards becoming himself a tyrant"

Actual hints in LOTR are really somewhat ambiguous about Denethor's theoretical final decision vis-a-vis Aragorn. He earlier told Boromir, impatient to be successor to a king and not just a steward:
Boromir: "How many hundreds of years needs it to make a steward a king, if the king returns not?"
Denethor: "In Gondor ten thousand years would not suffice."

Would Faramir (perhaps the key "swing" figure) have supported his father or Aragorn?
And what of the prince of Dol Amroth, the council, and Eomer?

Of course, it would be really interesting to include a survived Boromir, but that's probably just too much speculation.

And no, I don't think Gandalf would have smacked Denethor around.