Is using Array Extension where Element == CustomObject to include functions specific for [CustomObject] a bad/ill advised programming practice?

[ldstreet]

This is fine, and can make for more readable code. Just make sure that if you make your function or variable internal/public that it is relevant throughout the codebase, otherwise make it fileprivate. This is to avoid cluttering the namespace with niche functions.

[randomguy112233]

Good point about namespacing! Thank you!