Currently when planning a Sprint there are indicators about full size of the Sprint (e.g. 300 hours) and I know that in theory the agile teams should be cross-functional but in practice (and as it is clearly written in most PMI-ACP books) there is some level of role specialization.
So seeing that I'll have a 300 Sprint says nothing about if the Sprint is feasible or not, there should be a breakdown about how much task is assigned to each member like the classic JIRA "Version Workload Report".

So e.g. a short summary in Plan mode would be cruical so that we can plan a Sprint:

John: 30 hours (24 remaining)
Sarah: 40 hours (14 remaining)
.... (listing assignees with non-sum-zero of course)

This way i could tell that our current team can do the Sprint or not...

Current workaround:
1. Start the Sprint
2. Go to Work mode
3. Count manually using Assignee Swimlane
4. Remove/Add Stories so that the Sprint can be doable

It is extremely painful and when the customer is there (face to face planning meeting) is shameful, so usually we can prioritize but defer the final planning and negotiate the final Sprint plan offline with the customer.... not a real agile approach