Benna has drawn up three new retirement-savings models that he contends offer the same benefits as a traditional 401(k). One is best suited for married employees with less than $100,000 of adjusted gross income and single employees with less than $62,000 of adjusted gross income. Another avoids the payroll taxes applicable to employer contributions. The third model allows employees to sock away pretax contributions of up to $12,500 under age 50 and $15,500 over age 50, compared with only $5,500 and $6,500 for some other models.