I'm new to Kumoricon, but not to cons generally, having attended KubleiCon for two years and Otakon for another two. Lines are a big complaint. Of course, the best advice to con goers is to be patient and tolerant of the things other attendees must do to pass the time (don't get pissed just because people start playing "marco polo", etc.), but that's hard to do when you have arbitrary rules making the lines not work.
Hear, perhaps, the suggestions of an amateur economist.
Saying "you can only line up 30 min before" won't work. If it isn't enforced, you reward rule breakers. If it is enforced, people will find nearby areas to linger until the "legal" line-up time... and then you get a stampede. Not good. So depending on the popularity of the event, you basically have to go SS on your attendees, checking an ever wider radius for "cheaters". Far better to just let people line up hours before if that's what they want, and manage the locations of the lines.
However, there is another possibility. Wherever a line is the problem, money can be the solution. The lowest (adult) registration fee is $35. How about, when we come into the con, each of us gets a set of tokens, "Kumoricash" or whatever, broken up into ones, fives, tens (a ten, three fives, ten ones). Any event can have multiple lines: the free line, the one line, the five line, the ten line. You then let people in according to line priority, with those paying the most getting in first.
The tokens would reduce the need to line up early. You can show up an hour before if you really want to be at the front of the "free" line, or you can attend another (probably less popular) event while you wait, then show up with a five or ten in hand to bypass the free or even the one line. Fewer people have to line up, early, hence less sprawl. Additionally, it gives staff a metric by which to measure the popularity of events not only in terms of quantity (how long the line is) but also intensity (how much Kumoricash people are willing to put out to "cut"), allowing for better planning in the future.
Finally, if we want to provide a potential bonus for panelists and staff, people could buy more Kumoricash if they wanted to (possibly including even higher denominatoins if somone thinks they need it). The extra would go to staff and panelists according to some previously agreed upon percentage, with panelists maybe getting the extra according to how much Kumoricash they turned in relative to other panelists. I'll bet people would show up to training meetings if there was a possibility of getting paid some small amount after the con.