SaaS needs to have teams, projects, payments, auth, invites, and possibly be configurable for different 'types' of scenarios... projects could be optional for instance if they don't group actions by project, invites could be optional if anyone can join any team, heck even teams can be optional if you can't add multiple orgs but it's nice to have, say you run multiple brands or something....and want separate invoices with separate logos... etc...
I'm getting close to launch, thinking I might do it as a paid $9.99/month gets unlimited access to everything I do in the scope of the project. Might raise prices eventually but grandfather people in for a time. Or might do FOSS with addons that are pricier, but I don't like apps that do that -- I'd rather pay small fee monthly and use what I need depending on client.