I think Daredevil and Moon Knight would work very well as foils to Batman in Gotham. Batman's all like "this is my city" and is tyrannical over who he allows in as far as costumes and capes go. Having two guys that, in my mind, are equals to him, would really add some tension. Especially once Matt Murdock uses his super hearing to discern that Bat's is really Bruce Wayne! I'm sure Bruce would eventually find out who Murdock is, but it would take awhile for him to gather enough clues and evidence, whereas Murdock finds out just by listening to his heartbeat.
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in theory couldn't Plastic man work in the FF and they could make Sue leader...I know she's not a mega brain like Reed but to say she's dumb would be a stretch.
The FF could reshuffle, but it's not really them anymore. Whenever they've lost and added a member, something always feels off, and it's never permanent. Reed, Sue, Ben and Johnny are the Fantastic Four, and always will be.
I know, but it wasn't that good. I'd like to reset the clock, and have them reencounter each other. They both have very similar motives and modus operandi--using fear, and whatnot.