I was thinking about this the other day when someone mentioned it, and thought it made sense to keep the regular numbers since first time viewers need it for clarity. And while I'm still pushing towards the normal numbers (I mean, we have "R2-D2" and "C-3PO" in a language that shouldn't have those letters at all), I can see that non-traditional numbers would work as well. Think about Predator. We have a totally alien number system that doesn't even make sense but its obvious what is going on there.