SLA reporting considering time periods for business processes nodes?

I’m trying to set up SLA reporting for several business processes. The goal is to provide an SLA report on various business process nodes, where each business node can potentially have a different contractual service window with regards to service times covering out of office hours, weekends etc.
So far I have set up dummy services for each business process node to be monitored in order to be able to use the standard service SLA functionality for node entities as well, but I have also read on the community here that the different SLA templates that were available in earlier Icinga versions are not available in Icinga2 and time periods cannot be associated to services for SLA considerations to date.

What would be the best way to establish that with existing functionality? My preference would be to either get the calculation from the Icinga2 reporting feature or from database functions (we’re using a mySQL DB at present) and not use a separate tool such as Thruk as for example described here Create SLA availability statistics and reports from Icinga 2 monitoring (in Icingaweb and Thruk).

Thanks for guidance!
Best regards