Other than the usual subnet and routing issues, stringing trunk fiber between the switches sounds good.
If there are multiple firewalls and ISP's involved, you'll have to pay close attention to the routing topology, or reengineer to reduce the complexity.
If there is overlap in subnet usage, you might want to renumber one side. Using NAT internally will be an ongoing maintenance headache.
-- Jim Leinweber, WI State Lab of Hygiene