How about adding 1 new XML element and 1 more PowerShell command for OWA binding? That would enable the new SP2013 farm to come online and be connected to OWA all ready to go for users.
http://technet.microsoft.com/en-us/library/ff431687(v=office.15).aspx
PowerShell
New-SPWOPIBinding -ServerName [SERVER_HERE]
Input.XML
somewhere to hold "SERVER_HERE"? maybe
http://technet.microsoft.com/en-us/library/ff431687(v=office.15).aspx
PowerShell
New-SPWOPIBinding -ServerName [SERVER_HERE]
Input.XML
somewhere to hold "SERVER_HERE"? maybe
<OfficeWebApps Install="false"
ConfigFile="config-OWA-2010.xml"
PIDKeyOWA=""
OWAFarm="SERVER_HERE">