The key terms in "uniform" laws are "multiple party account" and "multiple person account." I scanned Michigan statutes for each and got a hit on the former, but it seemingly only applies to credit unions. Some states hide these provisions very cleverly; in Texas they are in the Probate Code.
Presumably the MiBA does new accounts training, the materials from one of those programs should take you where you want to go.
P.S. Even if state law allows naming a POD on a sole proprietorship, it may not be a particularly good idea. I've seen it done where it was a going buisness with several employees. The owner died and suddenly the business doesn't have a dime to meet payroll, pay the bills or anything else. The business was to be operated by the decedent's estate and sold to the son, but every dime in the bank account had gone instantly to the POD beneficiary, the surviving spouse. (The decedent probably forgot he had done it, but he certainly did not mention it to the attorney who helped plan his estate.)
Doing what they want isn't necessarily doing them a favor.
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In this world you must be oh so smart or oh so pleasant. Well, for years I was smart. I recommend pleasant.