You're forgetting Kyoraku is a smarter fighter than Kenpachi. His Shikai would be more than enough. I'm not saying that Zaraki wouldn't be able to learn the rules of the games as Kyoraku even explained it to Starrk so he'd probably do the same to Zaraki. Also, C46 considered him a threat to the Gotei 13, but not to Soul Society itself. Anyone from the Royal Guard easily stomps Kenpachi.
No it's not about being "worthy". Have you forgotten the procedure to attain Bankai? You have to force your Zanpakuto into submission, it doesn't matter if it "talks" to you. For example look at Zangetsu and Ichigo. Zangetsu was constantly lending Ichigo his power but even though they already had a solid relationship, they talked frequently and they trusted each other, Ichigo still had to undergo the Bankai training. So it isn't about whether the Shinigami is "worthy" or not.
Smarter fighter? So zaraki real sword skills is enough to deal with kyoraku shikai....ichibei is the only one in squad zero that's can clearly beat zaraki to me if current zaraki remove his eye patch I don't know what's going to happen an I doubt we seen the real ability of his shikai yet....so like I said if he gets bankai it's bye bye he will destroy everything even us.
Force it in to submission? Ain't that only urahara way of doing things?....anyway zaraki sword has pronounced been trying to talk to him for a very long time now where as Ichigo only knew his zan for a very short period of time an it won't even his real zan talking to him most the time so yea....an Ichigo hollow don't like him no way really I think or does he now?