See my more detailed answer here
https://salesforce.stackexchange.com/questions/71604/lightning-bug-in-lightning-framework-when-using-aurarenderif/72931#72931

The framework does support nested ifs, it's simply that it has a bug you appear to be running into.

Surround the content of the second if with a div if possible.

You could also make the first child after the if a div (style="display:none" even works).