Courses and course formats

Hi everybody-
I'm a Moodle newbie but I am very impressed so far. I'm a firefighter with a large urban fire department, with a large MS Access training records database kept at the fire academy. My current job involves a ton of work just to keep this monster working, and I will move us over to Moodle, with a just little help.
We (me and the academy's summer intern - a CS grad student, thankfully) have our basic setup running nicely on a windows box, with phpmyadmin, mrbs, and php acceleration added in. The intent is to begin with Moodle as a central record-keeping tool AND a repository for course presentation materials and handouts. Once it does that convincingly, and with less effort than what we have to do now, we'll expand into all the other features. So far, works GREAT.
Our difficulty is this: the academy training right now is recorded in MS Access with three key fields: userid, courseid, and completion_date. The course duration varies from 23 weeks down to single day seminars. The thing to keep in mind is the focus on the completion date - the "finish date" which we use to build each FF's master training record and produce college-type transcripts. (We are also a credit-granting agency with a full-time registrar.)
In terms of enrolling students, the six month courses and other "longer" courses work fine in Moodle as is. A student would only enroll in such a course once. The single-day training that we have is repetitive, though, and is scheduled in terms of firefighting units, not individual members/students. We know Engine 1 is coming for the drill, as scheduled, but the members working that day will be enrolled/recorded as trained only after they get here. A firefighter may come four times in a year for the same drill - "Tactical Unconscious FF Removal" or "Self-Rescue Rope Refresher."
Upon completion of the drill, a hand-written sign-in sheet goes to the data-entry person. Most firefighters and their officers will repeat at least one of the single-day drills during a two-year period. They are essentially re-taking a one-day class.
We've looked at groups, restoring courses, etc. and haven't found a solution yet. (One particular drill/class is conducted 300 days a year, and most training is conducted at least once a month.) The solution we desire will let the data-entry person, who is swamped, enroll anyone off of her backlog pile, some of it more than a month old, as well as the current 'today' students. It will let specialty instructors build attendee lists for future multi-week classes that are offerred 4x a year. And, eventually, regular instructors in the classroom will sign in to Moodle and before starting their refresher training Powerpoints or printing their new handouts, they can go around the room and take names/enroll students right from the podium.
In short, we need to enroll students in a course, then find and enroll them again in a new "section" of the same course next week or next month, and we need to back-fill 200,000+ training records across 20,000+ active/retired members within 400+ current/archive courses.
We've been tempted to add a training_date to the role_assignment table, then modify the assign.php/html files so when assigning the role 'student' for a course, the user will have to pick a 'section_complete_date.' (the date of training for one-day courses, and the "finish date" for multi-day or multi-week training.) As we say over the radio, "Can anyone advise...?"