Accounts on the dashboard have almost zero relation to accounts for billing purposes. You don't need any dashboard account at all to actually order things. You do need one to claim things. So GM can buy 20 switches, Buick can buy 20 switches and you can bill it all to GM, you can bill it separately, they can all use the same org, they can use a different org. If you are using a subscription you can have multiple in the same org, but each network can only have one subscription. So you could have Business A, with Divisions B and C . Each Division has their own subscription and different sets of networks, but perhaps some shared needs require the single org.
You could also have Business A and Divisions B and C each have their own meraki org.
If you use co-term you will have to order the renewal all at once per org and the licenses are all shared. How you bill to customer is between you and them.
I suggest you perhaps have a discussion with a Meraki AM or a Cisco specialist at your Distributor where you can get into more detail than a public forum. There are a lot of possible combinations of operating modes here and your customer base may require that you deal with all of them.
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