breloom"Mainstream" tf2 players will never play seriously competitive tf2 regardless of what ruleset you give it. I have met more than my fair share of people who expressed interest in playing, played with my group in pugs, etc for a couple of weeks, then disappeared, completely never actually ending up on a team (this is through MULTIPLE groups of friends, pub communities and otherwise). Most players who do stick it out and join a team never persist past the point of UGC silver. They simply don't have the time to invest into chasing invite dreams like the typical tftv poster does. Anyone who is competitive and loves tf2 already plays competitive tf2. Everyone else has either moved onto the next hotness (CS, Dota, lol) or will never ever play in ESEA open.
I highly doubt more than 10% of the competitive TF2 community seriously aspire to play at the Invite level.