I would be satisfied if I could delete the at&t branding.
That right there is probably one of the reasons why it's locked down.
We all know perfectly well how carriers have been slow as snail snot when it comes to releasing cyan/denim updates to WP..... It is not just about user security and prevention of hacking/viruses, but it's also about catering to mobile operators.
If I was a mobile operator, would I sell and support a phone that could allow someone to easily unlock the phone from my services and instantly jump over to the competition?
Would I want to support a phone that could allow hackers and even regular users to see code and sensitive information about my carrier service, etc?
When I add a phone to my service for customers to buy or put on a plan, I have a contract/agreement from the manufacturer to allow me to put my bloatware onto those devices and perhaps get more profit in the process..... Would I really want to add a phone to my selection of devices that could make it that easy for my users to remove on a whim?
It is not just the Users MS has to cater for, they also have to cater to carriers too so they can get their phones to those users through the carriers easier.
In the process, some sacrifices are required.
Comparing a phone to a PC doesn't work.... A PC is something you bought or built yourself and there is no carrier involved in what happens with your PC.
The closest comparison would be being allowed to hop onto the modem your ISP supplied you and being allowed to tinker around with all the programming on that.... Adding, removing files, changing values, hacking it, etc.
Ever try to disconnect the ISP's modem and swapping it for some other random one you bought in a store? Doesn't work very well.