I think you're not fully embracing the lean startup methodology.

Is your SaaS handling some operations that are a matter of life and death or critical mission thing for an organization?

if the answer is No start with simplest option and do a soft launch and invite some carefully selected (50) beta testers.

Get the service going and gather feedback as much as possible. Then when you're at version 1.5 or 2.0 you'd know the problem you're solving a lot better.

Slavi,
Orbisius & qSandbox