Client (husband) has Solo 401(k). Wife on payroll . She is opening Solo 401(k) as well.

S-Corp owned by husband. Wife is currently the only employee.

Husband and wife will hire a full time employee in May 2024. Can I implement a 1 year requirement on the solo 401k plan NOW, to continue eligibility for 2024 for the husband and wife? Essentially, making the newly hired employee ineligible until 2025 when the new employee meets the 1 year requirement?