Mr. Blunt has it completely correct. 1.5 to 2 hours is about three to four times longer than a game of any traditional RTS, and many people simply do not have the time to sit through an entire 2 hour game in one sitting. Especially with more ridged tournament scheduling. Also, what format shall we play? 4v4 or 5v5? Regulars like that, non-regulars not so much. 1v1 or 2v2? Now you've lost the interest of the regulars.
By 'stacked fleets' I'm pretty sure he's talking about unit diversity. Most people on ICO just spam the imbalance unit of the month. People will be playing to win in a tournament even more so than usual, not have fun. Do you really want a tournament where people rush each other with carriers every match? And don't pretend otherwise, I've played enough online games every patch to see how ICO regulars play. Balance needs to be somewhat stable for a tournament to showcase a game, and get the community more interested. Sins does not have that stable balance right now, and frankly never has. There's ALWAYS been one unit you can spam without thinking to win.
1v1 and 2v2 isn't quite as bad as 4v4 and up as feeding doesn't work there, and committing 100% to 'rock' is much riskier as there's no recovering if you opponent goes 'paper'. But will the regulars want a 1v1 or 2v2 tournament? Not a snowballs chance in hell.