Does the controller in port 2 on the Colecovision Flashback do anything in single player games?
I know they screwed things up so it won't be a plug and play, but it might be worth modifying a wired AtGames Atari joystick to keep plugged into the second controller port for games like Pepper II if this old trick still works. I know it's not an easy thing to get one of these Colecovision Flashback controllers working on the real deal (Unlike with the Intellivison version where a simple adapter has made these new controllers compatible), but I bet the troubles are mostly keypad related.
Getting an Atari joystick working might just be an easy rewiring job to change its pinout.
I wish the Sam's Club special edition had this along with its paddles.
But alas, if I want wired paddles which I do want (It's largely why I'm bothering with the FB5), I'm stuck with two more of these FB4/5 wireless joysticks.