I've been thinking since Gol.D Roger and Monkey.D Luffy are so alike what about their relationships with allies and villians.
Gol.D Roger= Monkey.D Luffy
Monkey.D Garp= Smoker (thought it was Coby before but he wants to be Admirial)
Shiki the Golden Lion= maybe Blackbeard.
If you think differentlly or have more ideas i'd like to see your post.