One thing that has occurred to me recently is that modern avionics seem to (potentially) require more head in the cockpit (unless managed and taught appropriately).
In the olden days when we only had 180 channels on VHF (100 kHz spacing) one could change from say 119.5 to 126.1 in a couple of seconds. Now especially with the smaller electronic displays it takes longer and more fiddling to change from say 126.225 to 134.175. I teach to change the whole MHz first and then have a lookout before setting the decimals. Same applies when changing ILS/VOR frequencies where with sets like the GNS430 I now have to find and press a changeover button before changing frequency. One of the latest mode S transponders require one to alter and then enter each digit separately and sometimes the transponders are sited on the other side of the cockpit. At one level this might sound trivial but it isn't in the sense that it encourages pilots to be more head in the cockpit. Add in the mix of other devices which many pilots use now and we have even more ingredients for not looking out adequately.
In fact you're much more likely to have a close encounter or a mid air in the circuit area than the open FIR notwithstanding choke points. Historically there have even been collisions worldwide within controlled airspace and I believe in the USA some time ago the statistics showed highest risk of midair was in airspace with mixed VFR/IFR traffic close to an airport which is equipped with radar.
Whilst I'm not a luddite I don't think this risk will be entirely solved by requiring all aircraft to have transponders with TCAS and/or be in receipt of an ATC service.