In Czechia we have sufficient capacity of ambulances and other emergency services. What happens is that off peak they serve to help move old people to hospital, like a super expensive taxi. In these cases I can see how "emergency Uber" could help. On the other hand the doctors serving in these ambulances are usually extremely well prepared, the best MD students go to study to serve there. Even if it is one in a hundred cases, they will recognize the stroke from a random chest pain. Replacing them would surely increase the death rate in these cases...

Sure but you can make such an argument about every single medical issue. People can drop dead in a few days due to an unexpectedly aggressive toe infection. At some point we need to compare risks to costs.

There will always be a trade-off between quality and cost. If you accept nothing less than highest quality (enforced by law and an extremely litigious society), then you get the US hyper-inflation of healthcare prices.

Also in the US, I think ambulances typically only have EMT's and paramedics. Though sometimes it can cost as much as the ER itself.