I'd like to be able to create a new User Account, using the existing Role options, but limit the access to only see/work within specific Event Buckets.

We have multiple active Event Buckets, and have a partner working with us on just one of them. I can't give them access to all the Event Buckets in our account (privacy concerns for all our data, order/people information, etc), so am unable to let them in to help manage the back end.