that's an idea!

that's an idea

That idea could work. A: "We could ask my brother to play music for the wedding." B: "Yeah, that's an idea. Do you think he'd be interested in that?"
See also: idea

ˈthat’s an idea!

(spoken) used to reply in a positive way to a suggestion that somebody has made: Hey, that’s an idea! And we could get a band, as well.