Engineoff,
Totally agree. As a jump pilot, i have lost count of the times where I have been running in to drop, and seeing a light GA type go scooting past at the same level, probably head down looking at the GPS!
Whilst a Para drop zone is NOT restricted airspace, pilots would do well to avoid, just the same as when flying through a glider site.
A 100kg projectile at terminal velocity WILL do a lot of damage to an aircraft, let alone the parachutist. (See the AAIB report on the Glider/jumper collision last year!)