I agree that a gamemode with a Detective would be cool, but I don't think it's necessary.
You need a Detective in games like Trouble in Terrorist Town because there aren't any meetings. In Among Us, the meetings make everyone a group of Detectives voting on who they think is the Impostor.
I think that a Detective would probably be part of a "Special Roles" mode that was going to be in Among Us 2, but will now be implemented into Among Us 1.
But, right now, the only way for us to see how it will really turn out is to wait for it to happen. I'm quite excited for it myself.
Innersloth Devs: Maybe the host can disable certain roles, and only make the Detective (or others) available?