We had them previously as a DS perk on most of our source games and removed them due to crashing issues... not sure if it was something that could have been fixed but it did contribute to server issues. This was a few years ago now...
I would not mind having custom player skins added to the server, however the trails for players, contrabands etc. should not be added. At first it will seem fun and cool you have fire or whatever trail behind you, but it is going to be annoying when 40 terrorist is jumping around.
I personally love the fact eGO has fast load times because you don't download things like this. I am not for adding player model skins/trails, at least in jb, because it helps CT's kill rebels when I don't think they should be able to. For example, if I stack with a player that has a different skin and I am rebelling, I will get killed from them knowing my skin and not having to know name.