None of us can presume to speak for him of course. I understand what you're saying like this, "how would you apply what you've learned from reading / playing Vincent's games if you were to redesign D&D?" which is a more reasonable question, I think. There are more things in Vincent's mind, WaitYes, than are dreamt of in our philosophy.
That said, according to the principles I gather from his designs, I'm not sure that keeping the fan base happy would be a huge priority. I'd rather somebody just designed an awesome game and let it be what it is, and let people decide for themselves if they like it or not. So much bad design in all fields comes from trying to "make people happy" rather than just trying do it right whether "people" are "happy" about that or not.
Also, the whole idea of a 5th edition of any game seems rather odd in the light of lumpley games publication history. Just like you don't see 5 different editions of Dogs in the Vineyard, but instead you get In a Wicked Age, Poison'd, Apocalypse World, and so on, it's seems to me that it's better to just design a new game instead of redesigning an old one. If one absolutely must keep the same branding and IP and so on, then fine, but make distinct games with distinct priorities that people can play or not as they like, (e.g. "D&D: Secrets and Spies," "D&D: Total War," "D&D: Epic Journey," and so on) rather than remaking the same old game and fragmenting your fan base.
All that said, the most D&D-like game that Vincent has worked on was Storming the Wizard's Tower, which may provide some insights. That one ran into some problems though, and then Dungeon World came out. Its core is basically the same as Vincent's design in Apocalypse World, and although the secondary elements were designed by others, the game is an homage to both Vincent and D&D, and in many ways feels authentic in both respects.