If you restrict eligibility from your retirement plan to a certain group of employees outside of the statutory exclusions (such as union employees or non-resident aliens), it might make sense to determine whether that exclusion is still proper.
Any definitions that are connected in any way with part-time employees can be a problem, especially since the SECURE Act allows long-time, part-time employees to become eligible for the deferral component in the plan. Exclusions from eligibility have to be reasonable, the days where you could exclude employees just on part-time status or by name are over.
