Any ideas on dealing damage from stuff falling on the characters and their hirelings?

In olde skool Warhammer RP we used the creatures SB & TB total (as a rough value of bulk) +d10 and used the T, no armor (falling rule) on the target.

Im thinking of using the same idea and add a 1d5 Impact Body Crit roll if at least 1 wound is caused.

What about other stuff... like large rocks, space debris falling dirtside, building collapse, falling coconuts?

Of course they also get to try and dodge per RAW.

Thanks

Later

*shrug* I'd just call it 1d10 damage per 50kg per 3 yards fallen with a +20 bonus on the dodge if they're already aware of it, +0 if they're not.