Agreed, radar is essenitial, and Inverness have taken steps to address the issue. The CAS topic is different in many respects, radar will protect you from the guy wearing SSR, but non squawking pop ups are a different matter altogether. If you look at Inverness, what exactly is that pop up, an aircraft or one of the many wind turbines which show exactly the same characteristics on radar.
Places like Inverness are merely trying to create a small 'known environment' where they know their traffic is safe during departure and arrival. The establishment of CAS should not in reality hamper other airspace users, provided you are willing to talk to the airport you're flying in close proximity too.