Legal Entity & Tax Structuring for the Acquisition of an S-Corp

Currently in discussions to acquire a company that is currently structured as an S-Corp and as part of the transaction, we'd like for the seller to roll some equity.

We currently have another OpCo and aren't really sure how to think about structuring the transaction. Our OpCo currently has a handful of investors, including individuals, disregarded entities, and multi-member LLCs.

Understanding that multi-member LLCs can't own