The problem with replacement batteries at powerstations is, how many do you need, and where, every station will need a large amount of them, they are currently complaining about making enough batteries with current demands, if we then atleast tripple or 10 fold the demand, the price will go up instead of down as now.
For racing it could be a pitstop, I am sure with the right system switching could happen under 10 seconds making it a real race option.
For normal daily use the charge time of 8 hours is not a problem, you as a person would spend less time recharching your car on a weekly basis then if you where to use petrol. Cause you only need to be there to plug in and later to plug out, which only takes a few seconds each time.
And as with most things motor racing this would eventually trickle down to the consumer. Possibly. It's a hell of a lot more likely to lead to a real world practical solution to the problem of limited range on electric vehicles than switching the whole bloody car.
Electric cars are still at a point in which they struggle to reach a 100 mile range before needing a 10 hour~ charge. For some people that wouldn't even cover the daily commute. Ideally they could create a battery with a 1000 mile range and maintain the 10 hour charge time, but until then replaceable batteries are a more sensible option to explore than replaceable cars.
Anyway, that's probably enough on an off topic topic. I think your suggestion was a good one, with higher real world potential than you gave it credit, that's all.