I think when we click on network profile link, which shows our network profile on for the Stack Exchange, we should also get tilled view of all the sites related to Stack Exchange. So that while looking at only the network profile, we can see, what all comments we got and replies and everything in proper format and if possible we should be able to personalize that.
If you login to Stack Exchange and look at that profile you can view your activity across all sites that you participate in. You can do searches and have custom tag sets. You can view your questions and answers from multiple sites as well.
Sounds like it can already do most/all of what you are looking for.