I think you may be surprised. If FFG were willing to throw in prize support (LEAST they could do; very least), it would really help. I believe the PP Masters is akin to this, no? I think that is fan-run, with prize support from PP. IIRC, it is also more popular than PP's Iron Gauntlet, which is that company's in-house ranking system.
This might be worth a shot. It would really help if FFG gave it love via promotion on their social media sites, prize support, etc. Would provide competitive games year round without having to step on the toes of league kits. However, I think FFG likes selling their Store Champ and National kits too much. I wouldn't see a reason they couldn't be incorporated into the scoring system, but, FFG may disagree.
Most tourneys get reported in some form or another somewhere. If not, c'est la vie. However, if FFG made it know to stores that XYZ site is interested in who finished where in their tourneys, I think they would report. Points could be given accordingly, and those could culminate in an annual championship.