It can be done, but I wouldn't, for the reasons stated above, plus the potential for vaccine reaction. If anything happens, I want a vet to be there to help. (That's also why I schedule the cats' vaccinations at a time when I can be home to observe them afterward, and take them back to the vet if they have any problems.)Adverse Reactions to VaccinationAllergic Vaccination Reaction
One of my cats has had a life-threatening vaccine reaction (anaphylaxis) before, so he needs to be medicated prior to vaccination and observed carefully afterward. A reaction can occur in a cat with no prior adverse vaccine response, so it's always better to be cautious - my cat had his reaction when he was 8 or 9 years old, and had been vaccinated without any problems every year before that.
Also, ther is a protocol for giving cats certain vaccines in certain locations in their body, so that in the rare event a vaccine sarcoma occurs, it can be removed (sarcomas in the back of the neck are difficult or impossible to remove completely), and it can be known which vaccine caused it.
There are many states in the US (mine included) where the rabies vaccine can only be given by a licensed veterinarian. Most vaccine catalogs will list the states where they can't sell rabies vaccine to the general public.