Hi,
Does the Cardinality depicted in the business domain model go well with the Use Case scenarios? If yes, then
you should not try to change it.
In my opinion, the use case scenarios are the things that you should stay true to. If there is a "marginal" change in the cardinality because you have to suit your use case, then you can always justify that change in the notes, saying that you've stayed true to the use case scenario. But remember - a marginal change and not a big one.
Thanks
Aditya