Battery swap necessitates more rigid chassis and battery, and probably would require more copper wiring - all add weight and cost.
It is because battery swap is not a constrain Model 3 design is lightweight more serviceable and cheaper. All qualities that are a priority over longer than 300 mile range which is also plenty for 90% of use cases.
For similar reasons I don't even think that Tesla Semi will swap batteries.
I agree that taking away this requirement offers a great deal of flexibility in bringing Model 3 to market. It might have been one of the compromises early on with Model S, not because Tesla wanted to take away battery swap, but more because they thought perhaps it would help if they thought they could, so they tried to get away with not doing battery swap, for the reason you stated. It follows the usual trend of corporations trying to treat their customers as cattle; it doesn't matter how long it takes to do transportation or achieve any life goals if you don't care about the customer experience, but then you're forced to figure out a way to soften the edges as you realize that it does affect the bottom line if you treat them too much like cattle.
For instance, when I was at my SuperChargers, I often could not find a bathroom, yet that is a 100% expected function at SuperChargers. Furthermore, SuperCharging was something that would lend itself to taking a nice meal when appropriate, but the food options at most of them were really poor, or alternatively, would have taken too long. And worst of all, there was no variation; each time I went to the same SuperChargers, everything was the same old plain jane thing. I'm not saying they wouldn't also have a bathroom at swap stations, but that's all they'd need, and not as much, either. Most people could then quickly get back in their car and find a really nice place to pull over and walk at. Granted, not all routes have a lot of great options, but many do. Being stuck in Mountain View, Manteca, Dublin or Fresno SuperCharger was awful, despite being around a lot of civilization in three directions. There's only so many times you can eat Subway or Pizza, or walk the isles of Target. And worse than that, when driving up into the Sierra Nevadas, the only SuperChargers were in basically the only places I'd not want to be: civilization, i.e., just the thing I'm trying to get away from. I know those are growing pains and making use of available resources during buildout, but it is a flaw in the design.
As for what to do about it, I'd suggest Tesla now study the problem anew, as the ramp up of Model 3 happens. If they keep aware of this during that time, then they can consider doing battery swap as the second generation of Model 3 and Model Y come off the line. I wouldn't be at all surprised to learn that Model S and Model X buyers have more of a relationship with their battery as an aggregate average than Model 3 and Model Y buyers who just want a decent transportation mode and don't give a flipping flying fuzzy about the stupid battery. I admit it would be ironic if in the future Model 3 and Model Y have swap stations and Model S and Model X do not, but I think that would also be an error: it is even more pertinent to 10 year Model S and Model X owners to want to not stop at the same old SuperChargers
again, and after being on their third or fourth Tesla, they might have gotten over their need for a battery relationship, and look at their batteries the same as their Model 3 and Model Y counterparts, basically as another battery to stick in their tool when the old one is depleted and needs recharging on the rack (just like electric hand tools).
One modest battery swap station with two stalls can turn over 24 cars an hour; one SuperCharger with 16 stalls can turn over about the same, about 24 cars an hour, with the same above-ground footprint. Double both, and the battery swap station above-ground customer footprint starts to drop in relation to the SuperCharger space. Battery swap stations are more expensive, and require pretty substantial underground warehouses in urban places or more likely large above ground barns in solar farm areas, and adjoining solar farms to charge their warehouses full of batteries, but swap stations don't have to be collocated with interesting stuff; they can literally be where the solar land is cheap; they don't even need drivable irrigable fields like farms, so solar can be on the side of a hill. No substantial fixed energy storage is needed; they
are battery warehouses, already, so all of their charging will be direct from sun, no A/C involved. At night, the batteries won't charge. There doesn't even need to be utilities around.
Who cares about the P100DL racer buyers? That's a different market, and I'm not addressing that. Probably they'd have more severe depletion accounting relative to racing, turning into more severe depreciation. I think they expect that with their price tag and intended use.