Hello Rahul,
one of our customer is running similar scenario without any problem. They have 2 CRM clients in the same system and 2 client in production system. We have even connected a single instance of SAP Contact Center (aka BCM) and it works without any problem.
The key thing is that you don't break the cardinality rule 1:1 of logical systems. And be very careful with developments, of course...
I think the multiple backed scenario does NOT apply here, because that is about 1:N.
Regards,
Dawood.