New DC Plan - lump sum payments

[richard]

Is there anything that would prevent a new profit sharing plan require immediate payment of lump sum benefits only if the amount of lump sum is less than $2,500 (not $5,000)?

Also, what would be the impact on 401(a)(4) testing if the same profit sharing plan allowed participants to receive their lump sums (above $2,500) immediately upon termination only if they are over age 55, while participants who terminate under age 55 would have to wait two years to receive their lump sum. During the two years, the lump sum would participate in investment performance of the plan. The catch is the only participant over age 55 is, naturally, the owner! I'm thinking about benefits, rights, or features here.

(The business owner's rationale is to prevent his employees from quitting work solely to get their hands on the lump sum. It's not a highly educated work force.)

Thanks