Thank you for you comment
Also, in the end even if users had a choice of which OS to install (which would already be insanely tedious to implement in a consumer friendly fashion), the OS would still remain on the phone, meaning that the end result would be the same.
This statement is a bit vague to me, so please correct me if I didn't catch your point correctly. OS choices are already out there. I have a friend who flashes a new ROM every week. So in my opinion, the customer could chose to flash the mainstream ROM, the manufacturer's ROM, or any other custom ROM out there. But in this case the software required to load these ROMs would be hard coded in a bios chip which makes a phone unbrickable.
Also, having to install the OS themselves on the phone would seem like too much for a lot of consumers, and would most likely push many of them directly to the iPhone.
I thought of that, but this option will make other customers more excited to purchase such devices (like me). After all, Android is mostly attractive for its customizability and this option would just push it to the next level. I do agree that in the end it's all about the number of customers, so in this case Google or the manufacturers should make some sort of survey to study the market's reaction beforehand. I think if a survey like this already exists then this idea was already investigated seriously but not considered. I never saw such survey, this is why I was interested to see your opinions.