Very good questions. As for immediate exchange unfortunately unless an online product is sold in box Stores like Bestbuy an exchange will take longer than immediate.
For online purchases it will likely come down to a variety of factors including online retailers policied & negotiated deals between manufacturer & distribution channel(s).
In an ideal circumstance having the option to have a warrantee resolved through a local channel to the consumer would be ideal and possible.
However it will take some time to setup ideal procedures to help expedite warranteed repairs & exchanges. Issues of day 1 received concerns like DOA or quality issues of course should have methods to expedite exchanges. This is also where its important to negotiate to have quality vendors that will support merchandise they sell without unreasonable delays.
The good news if a box store like Bestbuy carries PiMax products. Bestbuy here in Canada you can purchase (at a premium) bullet proof in store warranties. Just bear in mind in box stores you pay for the convenience to visit them personally.