This is definitely something that's needed. XAC is good, but false positives are more common than you'd think (when I've been playing with friends who I consider to be good at pvp on more than one occasion XAC has banned them for a minute- falsely, mind you). If we could improve the accuracy of the system, then it would get most of the hard work done, seeing as there's a backbone for such a system already there. Then you just increase the amount of time XAC bans for and we've got an automated system, much like anticheat and AntiSkid.
We would need to test it quite thoroughly though, as I believe the reasons behind the rare false positives produced by anticheat stem from a lack of initial testing with good players (basically, the people testing anticheat weren't 'good'). There will be a margin of error but it's all about making it as small as possible.
I suppose the ultimate way to prevent hackers (although even this way isn't 100% foolproof) is to force users to connect with a 'client' developed by MCGamer. It wouldn't let anyone who doesn't use the client on. This presents its own problems, for example; non-English speaking players not understanding what's going on, as well as it just being a general fuss. Not to mention anyone with decent programming abilities could easily modify the client and make it undetectable- much like how some hacks in CS:GO bypass the VAC system despite VAC relying on looking into your client files to find anything fishy.
Conclusion - no method is 100% foolproof, but we can endeavour to improve XAC to act more like anticheat or AntiSkid or look into other measures. Also, we have the staff team (although the community seems to be losing faith in us ;-
at our disposal to finish off the ones that get away from the system.