You need to build what Israel is building, not fences, but concrete walls. You would need a large (Millions) standing army to monitor the barrier. If I were OBL, I would love your barrier concept.
The fact that you an d OBL would like it, makes it OK. COntrol, COntrol, Control. If we can't control our own border, we can't control anything.
The searching of goods is paramount to finding weapons, druga and people trying to get into the country. Making things more difficult for OBL is good for America. Look at the job potential. This could be very good for our economy.
This could be done with the coasts also.
Where are you getting this number from? If we had a barrier that would be impossible to cross without some major engineering, along with motion sensors, then we could guard the border quite well even with the numbers we have (about 9000). Tripling that number (which could be done with very little cost, comparatively speaking), would make it that much more secure.