I’m sure this has been asked before: but what if Pet Sounds was a massive success? Topping the charts and the unequivocal best selling Beach Boys album at the time. Would Mike change tune? Would the rest of the band welcomed and accepted more change? Would Capitol be more willing to Brian following avenues he wanted to musically?
I'd suggest Brian accomplished that a few months later with Good Vibrations. Totally new sound, innovative, psychedelic, ahead of it's time, universal appeal to both the kids and the "heads", a massive #1 single that hit worldwide. Critically and commercially successful. Capitol was 100% behind it with their promotions, and also gave Brian the green light for the album he had in the works, agreeing even to have a more lavish album package including a full-color booklet, which for a pop band in 1966 was pretty much unheard of. This was before Sgt. Pepper, which gets credit for presenting a pop album in a more lavish, sophisticated cover design and packaging including cut-outs, a gatefold, etc.
So yes I'd say Brian had that clout on the back of Good Vibrations, it was a massive success and the label loved that it sold millions worldwide and hit #1. Various family members and maybe even band members, however, perhaps didn't like this "new direction" as it played out even though it was a proven success at the end of '66 going into '67. See the Vosse "Fusion" article for more on that.