Hi, is is somehow possible to set PathObstacles to be ignored by some characters?

No, its not at the moment. I believe though there is something on the road map for this.

In the meantime, I got around the problem by using two nav meshes. Then you can set different obstacles on each one. Your agents can then path on which ever nav mesh depending on which obstacles they can avoid. Not an ideal solution as you pretty much double your memory consumption, but it does work.

Speaking of which, the recast library actually has a few great features that haven't come across yet into EE, such as uniform random point selection and off mesh links, just to name a couple. Esenthel, if you're reading this, exposing the random point selection feature would be pretty useful.

Recast also has flags for its poly, and has convex volumes to prevent agents from entering or passing through them if they don't have the right flag set.

Thanks for informations. It will be good if Esenthel will add this features in the nearest future. fatcoder's solution looks nice, but I'm worried about the drop in fps especially I found yesterday some bug in my codes deleting which gave me almost 2x bigger fps in some places and I don't want lose performance again.