I was wondering if you can use root access to relaunch an app as the root user? Say launch->check root->user->relaunch as root->check root->start root activity. This could be useful to prevent toast spam.
If you can get root in your app, you might be able to relaunch as root. But if you are doing a lot of small operations with su you will get a toast message saying the app got root. I have had them last for minutes.
Then you need to build a custom ROM which enables Android to launch apps as root.
I doubt it will stop the toast issues, anyway, as apps that request root always shell out to SU.... None of them are expecting to be launched as root.
Probably best to just disable notifications in your SuperUser app. The only issue is that the setting gets reset when the app is updated. But you can see why that's a good thing from the security viewpoint.