Reporting on all employees' appointments

Morning everyone! First post here so go easy with me!

We have a new requirement in the organisation to be able to report on how ~500 of our front-line staff (grouped into separate teams) engage with customers and other members of the public.

I'm wondering whether this could be achieved using Outlook Calendar appointments and then reporting on this in Power BI using Graph apis?

For example, I go and see person x at location y, and the stuff that gets discussed is added in the appointment's description. I categorise the appointment using pre-defined categories (for example "Community","KIN","Adhoc") 

Is it possible, using Graph's apis (or some other M365 magic) to report on a whole team's appointments of this type, determining how much time has been spent at "Ad Hoc" appointments, how many have not been "Community" appointments, who has had the most engagement in minutes this week, etc etc. 

Taking it one step further, there are weekly, recurring engagement requirements. Could these appear on all team members' calendars until one of the team completes the engagement? (Can tasks be in appointments?)

We have Power BI, so could the data be presented directly here, producing graphs and other visuals automatically for the management?

Any thoughts / ideas welcome, and signposting to documents to read is also encouraged!

DJ