Ok, a chained app is definitely the way to go for your selections. There are a few ways about doing this, but ultimately you could have two list boxes in the second app, one with current selections and one with selections not chosen in the previous app.
Regarding the radio buttons, this describes a good use for the Detour Tool and Tool Containers, having two apps
may not be necessary.
Finally, could you post your feature requests to the Idea Center? This would ensure Product Management sees them.
Thanks!