Save them for another story or sequel, otherwise, kill your darlings.
From experience as a reader and writer, redundant and interchangeable characters in a story will confuse the reader and reduce the impact of your lead roles. Find a few good reasons to keep some as background characters and ditch the rest. Then when you’re into the editing phase, i.e. when you’re making the story good, you’ll likely find reasons to subtract instead of add more characters. So if these extras really seem cool to you right now, save them for another project where they’ll have a chance to shine.
In yawning memory of Marta, Brandon (Brad?), and countless other extras I’ve sacrificed in the name of storytelling. I’ll never remember why I felt you were necessary.
~ Thanks for asking!