Voted 1 and 4. To me, "regular difficulty" implies a whole host of other things than difficulty: it implies, chiefly, that it is a tournament that a standard college club ought to send a team to (as opposed to a "novice" tournament, which clubs struggling for recruits may opt not to attend, or a "nationals" tournament, which clubs may not qualify or feel ready for), and that there should be enough such clubs to make a field of all college teams possible without open/exhibition teams.
I also agree with Mike that if you're an open tournament, you should be able to target whatever difficulty you want. In fact, if we are going to allow open/exhibition teams during the season at all, I am very strongly in favor of converting a so-called "novice" tournament into an "open" tournament with performance based eligibility restrictions instead of student status (e.g. undergrad/grad/not in school) based ones. There is probably a huge class of former players out there that don't play a lot because they were never good enough to score more than 1 or 2 total tossups at a Minnesota Open, or they played a long time ago and their top-level skills have rusted or become obsolete; sadly, that's the difficulty level that's available for them to play.
UC Irvine 2008-present; UCLA 2004-2007; Capistrano Valley High School 2000-2003
"It's a competition, but it's not a sport. On a scale, if football is a 10, then rowing would be a two. One would be Quiz Bowl." --Matt Birk on rowing, SI On Campus, 10/21/03