Are you maintaining Distributers in your system?
Now, It is your call. Do you need Distributor access to your system? If Yes, for that purpose you just need to create a model-driven app and shared it with external users. Right now it is working with any free licenses. first, resolve their access and assign them leads.
If you do not want access of distributors than email is fine.
It is your call whether to create new power automate or extend an existing one.
Let me know if I can provide you with more details
Power Platform/Customer Engagement Developer/Lead/Solution Architecture/Project Manager