I understand he good intention behind this action. However, personally I'm not sure how practical this is. Some of my points are below -
1. Many times people ask questions that are extremely simple and nonoffensive in which case waiting for approval seems very fraustrating and meaningless.
2. Many times there are questions of which people want to know the answer urgently. In such cases, delaying the post may be too late and may not serve its acual purpose.
3.
IN GENERAL, the majority of threads are harmless which are posted by members of the forum who have been here for a long time with good reputations and sometimes occationally some threads may be inappropriate or offensive. What I'm trying to say is, in any islamic discussion board, generally there are far more positive threads than offensive or inappropriate ones.
Therefore, in my opinion, its far easier and less time consuming to delete offensive/inappropriate threads than screening ALL the threads before approving.
4. If you are too worried about external links within the posts, then perhaps you can write a script (I guess its possible!) which will check whether the new thread contains any external links or not. If it has then it can wait for approval otherwise it can be posted immediately.
These are just my thoughts on this matter.
Jazakallah Khair.