Are we really discussing about making airliners tolerant against landing on the engines and still being able to fly away afterwards???
I was thinking of a pod strike whilst the landing gear was extended rather than doing a touch and go on the engines. On a B737-200 you'd have to work pretty hard to scrape an engine on the runway, Airbus thoughtfully gave a decent clearance for the IAE and CFM engines though this has reduced slightly with the NEO. The B737-300 had to have the lower cowlings flattened out as the clearance was so poor. With the longer wings of the four engined jets, a pod scrape on a outboard engine was quite possible but you would hopefully still have three undamaged engines and ancillaries.
My point is that with lower ground clearance due to higher bypass engines, and twins now being the norm, the chances of a strike are higher and the risk is that 50% gets knocked out rather than 25%. With this in mind it might be worth looking at the figures to determine if it's still acceptable to mount certain components in harm's way.