Isn't much FOD ingestion due to the wheels kicking up something? If so, mounting the engines in the back seems like a bad idea, as even if they are higher up than an under wing mounting there's a risk that the wheels might kick up some debris?
See also SAS flight 751, where ice broke off from the wings and were ingested into the engines https://en.wikipedia.org/wiki/Scandinavian_Airlines_System_F...
From a FOD perspective, in my admittedly very non-expert opinion the best location would be to have either a high mounted wing with engines in the traditional under wing position, or then engines above the wings like the Honda business jet?
