No problem! Just increase your pledge amount by an extra $30 and specify that you're doing this in the details of the pledge. This also works if you're looking to purchase additional upper-level reward tiers.
Upon campaign conclusion, we'll send out a survey asking all members of that tier to arrange all 19 classes in the order of their preference. We'll make a point of trying to get every backer used for at least one of their top three choices.
That's up in the air right now. We intend to support the system after it's initial release, but the particulars are dependent on the publishing process and initial reception. This Kickstarter will largely determine if we seek to publish more comprehensive physical books, or support the system through releasing splatbooks in a PDF form.