My understanding so far:
We would prefer to implement this via custom code instead of VISTA rules.
Is it possible to send data to a different organization's suite?
Yes, this is definitely possible. Just make extra sure you test and validate the data in both report suites in a dev environment before rolling it out Live.
I believe you can, in the same beacon, only if they use the same data center. Not sure about the billing implications, though (do they both pay the secondary beacon rate?).