Ok I just wanted to update to respond to the last suggestion about using regions, After this I will let the topic retire.

I started to test out the possibility of using regions, but this also would require as many region checks as their are types of regions. For instance, If I had 20 different regions set up with different behaviors, that would be 20 region checks each frame. Where as detecting passable_ent was only once c_trace / c_move, which were already being called by the movement code. This was also more flexible as the skills could be used to change the behavior, with limitless combinations. Helghast's solution would work great, if that event would trigger when inside of another entity.

Perhaps if c_trace could return region information, or if a function could be created like ent_region, which returns the name of a region a specific entity is in... But alas, I would prefer passable entity / block detection with the new format. Thanks for reading and replies