I'm not very familiar with your plugin so far but it seems to be the best place to enable IDN Support also for other plugins?
I just wrote some simple piece of code to enable IDN Support in the 'WordPress MU Domain Mapping' Plugin but I'm not sure if the maintainer is going to use it, or if it wouldn't be really better to export this function into one IDN enabling plugin like yours.
It's discussed here:
I don't think it's useful to wrote for every plugin an additional IDN enabling script. So if it's outsourced it's in my opinion the best place to put it in your module.
Do you agree? I know it could have some side-effects but they should be not that big and it improves your plugin and it's much easier for the user.