Read Only (Score 1)

If no is not a sufficient answer and you can not come up with a legitimate business case the a replicated DB would be my choice.
Possible business case reasons:
No way to prevent access to other customers info without significant development time and expense
Server may not be able to handle the expanded load
Not enough licenses for the server

If you have to
Charge for creating the replicated data
charge for development time to provide access
charge for service of maintaining replicated data
write read only views to the data restricting what they actually have access to.