[Lizard]

I'm not sure I understand the desire for this. One of the philosophies of OmniFocus is about having everything you need to do together in one place, so that if you need to run errands for work and home, you can see them both together in your context lists, even though they're for separate projects.

Many people have a Work folder and a Home folder with separate projects under each.

Holding down alt when starting OmniFocus on the Mac is primarily available for testing and troubleshooting purposes, not because we expect users to actually maintain multiple databases.