Well I'm sure that the Aeromods & electrical charging mods produce benefits, but a second look will allow us to see just how much improvement is gained for the money & effort involved.

Electrics
Parasitic drag. This is the mechanical drag form the alternator just to turn it over. This will not change regardless of whether it is charging or not.
Electrical load. The electrical load is quite high at night, just after starting a cold engine as the lights & starter suck a fair bit from the battery & the alternator needs to replace any lost charge from the battery from the starting process, & to provide the electrical needs of the running car, but in broad daylight, after the battery charge has been topped up after starting, the only electrical load should be the ignition, blinker & stop lights, all of which is quite low & in the case of the lights, intermittent.

By all means, use a switch to cut off the field current, thereby stoping the alternator from charging as it will be cheap & easy to do, but I believe that the savings will be almost unmeasurable.

Aeromods. The shape of a B210 is fairly slipery anyway, however, unless you can make a slipery tail from some thick cardboard & duct tape which would be fairly easy & cheap, then this course of action looks like being a bit of a dead end for a car that is used very infrequently in economy trials, while spending the rest of its life as a performance car or an ice racer.

Permanant aeromods will be more costly, difficult to do & will leave a contraversial shape that not everyone will think of as being 'cool'
As for fuel savings, these aeromods are really only of significant benefit at speeds where the car was suffering from substantial drag in stock form.

At the low speeds that econo-drivers travel, I don't think that the aeromods really produce worthwhile benefits in the majority of cases, but if they can be done easily, cheaply, in a temporary fashion, & do not damage the car in any way, then give it a go.

EMIS. As the video clip shows us, the trucks in the clip can recoup the investment in two to three years of continuous day-in, day-out operation. This suggests to me a very high initial cost, & when used exclusively in occasional weekend economy runs, the investment would be recouped in about two centuries, so I suspect that the cost/benefit balance is not very favourable, particularly in a car that lives the rest of its life as a performance machine.
I wonder how much the extra batteries & the 48 volt charging system weighs, & how much edditional electrical load is imposed on the charging system to top up the batteries after the system has cut in after climbing a hill, for example.

Keeping in mind that these economy events are for sporting/educational purposes without big cash payouts for the winner, then very low cost improvements are probably the best path to follow.

Hmmmm, I wonder if some plastic rear wheel opening covers that are duct taped on will yeild in terms of efficiency. Worth a try I suppose.