I think Rilian would definitely need assistance for a good while, just getting back in touch with the small changes in Narnia that happened while he was gone-the kind of things you don't notice while you're there-not to mention the international scene. Caspian being elderly and without an heir must have played hob with politics, probably weakened Narnia's front among certain other countries because they could see possible war coming, etc. (I bet Calmoren was excited, heh.) I wonder how many treaties started to unravel, there at the end when Caspian took his voyage? Trumpkin was regent, but not everyone would have accepted that as being valid, or as being *enough*.
I liked Rilian, once he was free...his nature seems innately noble, and brave...I don't know if he was naturally grave or if that was a by-product of his travails, but he reminds me of Edmund, in a Horse & His Boy. That same grace.