And that's probably why we do not have a collision model - because ppl can turn them off.

Solution would be to implement performance-friendly (simple looking) trees as option, remove the "tree-off" option (after proof that these don't impede performance for weaker machines) and equip all trees with a collision model.

My guess however is that we will have collision models only in a couple of years when the weaker machines have disappeared or have become marginal.