You can get data from the members of a group, and even loop over that data, but you cannot set data on individual group members. I’ve seen this question come up on several forums, mailing lists, and beta lists. You can’t store a reference in an attribute (so you can get it later and plug it into Set Data). You can store a string (eg the object name) in a string, but you cannot convert a string into a reference. And you can’t plug your Get Group into a Set Data.
Things like references and execute ports are part of the pre-evaluation stage. They must be resolved before the ICE tree is evaluated. Everything else in the ICE tree is the stuff that has to be constantly re-evaluated. So driving a reference port with another ICE node doesn’t really fit into the way ICE was designed to work.
For something like (resolving connections), you’re better off using a script to set up your ICE trees.