ASSC certainly looks promising but a couple of issues....
To take full advantage of it, aircraft will need both ADS-B in and out. Airlines are fighting the out mandate. No anticipated mandate for ADS-B in. That may be market driven with numerous programs for reduced separation based on having both ADS-B in and out.
Also, for maximum protection, the aircraft should be the source of any warnings. This is possible with ADS-B (I served on a ARINC/MITRE committee researching this some years back). The problem with a ground (ATC) based system is the inherent delays associated with:
(1) recognizing the issue/conflict
(2) issuing the warning to ATC
(3) delay in interpreting the warning
(4) issuing a warning to aircraft involved (with the potential for transmission being "stepped on" as in Tenerife).