Advice needed for using multiple OUs in Payables

I need to begin paying invoices for a second company in Payables.  Both companies are set up under a single legal entity and ledger.  I thought I could do it using pay groups but the issue I have is that the liability account string is different for the two companies so, I am thinking I need to set up a second operating unit for the new company.  I am looking for any advice as to what to be cautious about and what to consider before moving down that path.  Are there any gotchas that I should know about?  We are