Want to pick the brains of this knowledgeable community.

What are some good ways to structure a small seller equity rollover (e.g. 10%), in particular with the goal towards giving the seller a path and visibility for the future sale of his rollover portion? I see two problems: 1) a math problem of the seller’s rollover equity value having a much lower value post-transaction due to the buyer putting debt on the company, and 2) ways to give upside to the seller for this rollover portion if the company performs well that does not violate SBA rules?
For the first problem, assume \$5m purchase price (cash free and debt-free basis), stock purchase, and 10% seller equity rollover. That means the equity being purchased by the buyer is \$4.5m (\$5m * 90%). For this purchase, assume the buyer will finance 80% of that amount, so the buyer will contribute \$900k (20% * \$4.5m) and will finance \$3.6m (80% * \$4.5m) in SBA debt. This debt will now presumably sit on the company’s balance sheet. So the new equity value, on a 100% basis, post-transaction will be \$1.4m (\$5.0m enterprise value - \$3.6m debt that has now been added to the company). So the seller’s 10% equity stake is now worth only \$140k versus the \$500k it was worth on a debt-free basis. Seems very unattractive for the seller.
For the second problem, barring another future sale of the company, how to give a path for the seller to exit out of his remaining 10% rollover if the company performs well and in a way that doesn’t violate the SBA rules? For example, giving the seller a put option to sell his remaining stake at a pre-agreed EBITDA multiple in X years makes sense, but will violate SBA rules if I am not mistaken.
In summary and taking into account the above, how does the structure and math work to make it attractive for the seller to rollover a portion of his equity (e.g. 10%) given the above math?