Does the following sound like a legit plan design?

For its annual profit sharing contribution, employer wants to contributes company stock for participants until they hit both age 25 and have 3 years of service. At that point, the contribution gradually involves less company stock and more company dollars. Eventually, at say age 35 and 10 years of service, the participant no longer receives any company stock for the profit sharing contribution, just all dollars.

Is this acceptable and if so, how would it be tested for non-discrimination?

Thanks