Re: Ryokugyu, I'd like to point out something about him.
His Justice is apparently called "Determined Justice" (死ぬ気の正義, Shinuki no Seigi?, VIZ: "Justice if it kills me") as per SBS 106.
I also recall that in SBS 76, one person asked if Fuji and Ryo were opposed to the WG in some way because of their animal motifs, and Oda didn't outright deny or confirm it.
So I would not be surprised if Ryokugyu's subservient behaviour is an act, or if, at the very least, he has some strong dream or ideal that persists regardless of his sycophantic behaviour.
Re: Kizaru, I don't know if it qualifies him fir Conk, but at least he is certainly a good leader and favoured by his soldiers.
Personally I feel like he is the Bertholdt Hoover of OP despite being more like Zeke in personality.
Kizaru's general theme is that he blinds himself to the evils of the WG, and I would not be surprised if there was a reason for that beyond his monthly paycheques like a misguided belief in some greater good.
And just like Bertholdt became an absolute threat when he became more decisive, I think Kizaru could also end up transforming into something similar, depending on what Oda does with him.
So I would not be surprised if it turns out that he
does have Conk, but only to a weak degree, and is able to master it once he undergoes some character development and decides what to truly fight for.
So yeah, let's see how it goes.