The major argument against sniper in this thread seems to be revolving around skill discrepancy and new players, but I think you guy are missing what the demographic of tf2mix actually is... While it's true that it was intended for new players who can't get picked in pugna, and after playing ~400 games on tf2mix I'm gonna have to say that a very large portion of the demographic is not new players. Pugna is dead nearly the entire day before 9 or 10 EST, and even then, it's mostly invite players getting picked, which leaves IM and Main players around to go play in tf2mix.
I've played many captain games where every single person is an IM capable player, not new players. Perhaps a pregame vote to re-enable sniper would be beneficial, if you guys are adamant on keeping sniper banned.
Also, I'm still not understanding why you aren't just banning people abusing sniper. If someone is going to be an idiot and ruin a pug on sniper, then they are going to be an idiot and ruin the pug on any class.