Action Center Licenses for an unknown amount of users

We’re in the process of automating a HITL process where the someone from HR and managers need to interact with the bot within the process.
The flow is something like this: HR kicks off process and inputs data → Bot works → Manager inputs data → Bot works → HR checks results → Bot continues working → Manager checks results → etc.

Usually a process like this screams ‘Action Center’.

The major problem I have is the licensing for Action Center. I cannot buy a license for every manager that might (or might not) be involved in the process for obvious reasons ($$) and I do not know how many different managers will be part of this process. It can be 5 or 100 in any given month.

Do you have any solutions for a problem like this or do I have to solve this without action center?