It’d be easy to solve this problem if the company weren’t cheap and the instructor union would allow it.

Hire line pilots as instructors like UAL. They get paid 9 yr FO pay, bid a schedule based on instructor seniority, work a turn or 2 a month for currency and return to the line usually when they can hold a CA schedule they want.

You can use the normal instructors for ground school and initial/upgrade. Line guys do CQT, CKA do type rides and LOE’s.