Why would I get tired of your ideas? That's why I posted here!
We could eliminate pump 1 and use a simple logic program to mix the two sources into the attic tank. Would need a level transducer in the cistern, then.
The attic tank would have 8 or 9 feet of head, giving us 2.5 to 2.8 PSI to the toilet. Wonder if that would be enough to operate the toilet fill valve...