I feel you are in a very high level league here, playing a higher level than I could ever do, but I can't help but have a few idea.
If your reports and their reports have projects that follow a similar pattern, maybe you could just track certain key points in all of them.
I would think you could require everyone to report their plans and work in the same format, then have info sent to you at specific intervals.
Maybe certain staff could be "experts" n certain points in the projects and review them for you using a criteria you develop.
I think the critical thin is what parameters are meaningful to you. When these fall above or below a certain value at a certain time. then you need to do some more careful monitoring.