As someone who has visited (but not explored) Chiba, Tama and Kanagawa I wouldn't feel comfortable giving out this advice.
Like the OP, I'm a repeat visitor who mostly stays in Tokyo.
Perhaps you can help me with this "explore Chiba" suggestion.
I'm making up plans now for an April visit. Disney Sea is in Chiba. But that hardly counts.
I also want to go to Nokogiriyama. But it seems the best way is to go via Kanagawa and arrive by ferry.
Chiba is a huge area. You've insisted that it's worth exploring. Could you help me out with a rudimentary itinerary? I'm just looking to know what the highlights are and what you thought of them.
Thanks in advance.