What problem do you see that would prevent you from doing it? It's difficult to address your concerns without knowing what they're.
As I'm looking into the documentation, the key difference seems to be that you'll set Web service URL and login details to your middle-tier service instead of a MyInvois environment.
I don't know the particular scenario regarding IRBN, but it sounds like you want the middleware to communicate with IRBN (using its Client ID and Client secret), while F&O will communicate with the middleware (using middleware's client ID/secret or some other authorization mechanism).
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