Actually, that's basically how we worked it at a dojo I used to train at. Now, it wasn't Aikido, it was sort of a composite, and the fact that it was university affiliated made the semester/year breakdown very natural, so I don't know exactly how well this would work elsewhere...
Anyways, for one semester, we would work all sorts of variations on arm bars (Ikkyo, roughly speaking). Usually only one, possibly two techniques on any given day. The next semester was nikkyo and kotegaeshi variations, and the third would be sankyo and shihonage variations. Lather, rinse, repeat.
Generally, we had a training regimen that was 2 days a week of the throwing stuff, then one of striking or ground-fighting (alternating semesters). One for free-practice (almost always throwing), and one on occasional weekends for bo. I really liked this way of organizing things... it appeals to my regimented way of thinking.
But more importantly, (again, this can only be applied in university settings), it was understood that if you couldn't come to practice regularly, you shouldn't come at all, since that would retard the group's progress as a whole. So, if halfway though the semester, you missed a few classes, you were really expected to drop it and come back the next semester. It kept the training really very intense.
And don't even get me started on the testing regimen....