Allowing end-users to "white-list" sites that they trust to take over the cursor would probably work - but unless it becomes mainstream HTML5 and is implemented on every browser, it's not very useful. There is a general resistance out there to options like this that require the end user to decide whether they trust a site or not because after enough sites have asked for permission, a large percentage of users get fatigued with thinking about it and just click the "Yes" box whenever it comes up.
But if it were to happen in both the Mozilla engine and WebKit - then it would certainly go some way towards fixing the problem.
However, there is still going to be an issue for touch-screen users - you can't reposition their fingers! Hence, we still need to figure out an alternative way to handle this - and once we have, we won't need this feature for desktop machines.