Managing a High Performer

We define our staffing needs by SoW and level of experience required. Level 1 junior to Level 4 advanced, etc. In a team environment, in many cases a high performing 2 may over run a weaker 4. This drives discussion of that T2 taking on the lead role, etc. The issue is we can’t just promote staff with limited depth of experience in the field, because they are strong in taking ownership of work. i.e., Promote a High perfroming 2 to 4 in 1 and half years in the field. Etc. Basic Quals for a 4 may align to guideline of 9 years in the field. How do you balance the "guideline" of years’ experience required for promotion and advanced responsibility, versus high performance in the role. The concern would be the precedence you set with an aggressive promotion. This may display a sense of inequality across the team in regard to promo potential.