In any case, how's this for a primary schedule. Going with some very approximate numbers and times, you start out picking the eight sates that had the highest proportional voter turnout in some previous election. You schedule those ones first, about two a week. After finishing those, and possible with a short break for people to consider and candidates to campaign, you have three "super tuesdays," with about 14 states in each. Every year you rotate that around so every three years each state gets to be part of the first super tuesday.
The details could be varied quite a bit, but that's the general idea. The "some previous election" could be the regular election the previous year, the previous congressional election, the previous presidential election, or the previous presidential primary. They'd have to pick one and stick with it of course, but which they'd pick would depend on which election they wanted to generate extra turnout for.
This way states like Iowa and New Hampshire that take pride in being first can stay that way... as long as they're willing to work at it. I've heard that they take their responsibility very seriously and actually study the issues involved more than most voters, which is awesome if its true. However pending the development of a large scale mind reading device voter turnout is the best easily quantifiable indicator we currently have of how seriously the voters are taking the election. (That i know of anyways.)