Anyway to put things in perspective, Metal Gear fans took David Hayter being replaced a lot better than Gundam fans took Saeko Shimamu's replacement and even if a creator has the right to replace someone it's probably not going to be taken well if that person's performance was well received, especially when it's done this way.
A better example would be replacing the legendary Shuichi Ikeda as the voice of Char Aznable. Just imagine what would happen? Bamco animation studio would've been
EATEN ALIVE
If Kojima's artistic direction is soo important, then why not replace Akio Otsuka?
That reminds me of the award show where Keifer picked up an award for Metal Gear since Kojima couldn't show up. IIRC Keifer was glad to accept it and thought the fan feedback was amazing and all that but it didn't seem like he wanted to interact any further other than working on the game and accepting the award. This is no mark against him since he obviously doesn't have to get knee deep into MGS if he doesn't want to.
But like you said, when you look at Hayter he was(is) directly linked with Metal Gear Solid and is synonymous with Solid Snake and interacts with the fans. There are plenty of voice actors that participated in all the MGS games but Hayter is the one that is mentioned the most out of them all.
Considering that, it naturally makes sense that if Kojima wanted to replace Hayter early on that that kind of popularity would not sit well when ruminating on that decision.
In the end I still associate David Hayter with Snake. Keifer only voiced Snake for one game while Hayter built him up in my mind from the beginning. One thing I'm curious about though is that if Snake does show up in a future game somehow I wonder if Konami will hire Keifer again or David Hayter.
If David had been on MGSV, then I guarantee you this is what would've happened:
The Best Timeline (wherein David voices Snake in MGSV)
1 month after the game's release
Kotaku's Exclusive interview with Snake VA David Hayter wherein he talks about that twist
KOTAKU: So, fans didn't react well to this twist.
DAVID: I understand their anger and I sympathize completely but you gotta understand Kojima's mindset, he---
3 months after release
GameInformer Interview w/ David Hayter
GI: Thanks for being here, David, I've got a couple of questions for you
6 months after release
IGN: Exclusive 90 minutes podcast with David Hayter, he answers all your questions and let us know which Konami Director may be a secret fishman.
David: Glad to be here *claps hand* Let's do this~
IGN: So, first off...what the eff was that twist?
The Worst Timeline (the one we have now)
MGSFAN
@24Power I didn't like that Venom Snake Twist.
(
24Power
@MGSFAN Who?
MGSFAN
@24Power You know, Venom Snake? The character you voiced in a videogame?
24Power
@MGSFan Oh..now it's coming to me. I think I did some voicework for some pervy wierdo. Don't remember much of it.
HIDEO_KOJIMA_EN
@MGSFan @24Power Some 'pervy wierdo'?? He likes me! HE LIKES ME!
24Power
@HIDEO_KOJIMA_EN Who the fuck are you?