It seems to me like you could model the first system tolerably well by having one person represent multiple centuries. So one lucky student gets 10 votes, the next gets 5, the third through eight each get 1, and then the remaining eight students get one vote between them. The net effect is that the vote of the rich "First Class" student matters a great deal, the various intermediate upper class people don't matter much, and then the "Capite Censi" don't matter at all.

If you also slap on Tribe labels, and then mix and match a little, you can model both systems.

It's not perfect, but the point is that by running through it for 5 minutes, you can get the feel. You can then quickly point out the actual numbers, and the fact that your model system underweights the power of the elites, and move on.