What I would like is a bootloader that has the following features:
* End user management of trusted keys
* Keep most major manufacturer keys pre-loaded (even if disabled for current use)
* Factory reset online, not from device contents.
When a 'factory reset' or other base-reinstall is requested, look at an indirect URI associated with the preferred active key (this means WiFi, Ethernet, or other network connection must be made). Similar to how SYSLINUX (in various flavors) looks for different identifiers from specific to generic, query for an existing 'file' that matches the device model and serial / MAC in a pre-defined way. When a possible file is found download the bootstrap, validate that it is signed with an allowed key* (if it has a valid sig, but the key isn't allowed, ask the end user), if it's valid run downloaded bootstrap.
The downloaded bootstrap should, ideally, validate and re-configure the flash layout, possibly update system firmware if desirable, then apply the current version (or maybe offer a choice of back versions if applicable) of the 'factory' image for the device.
This way updates to the core image can be shipped with factory resets instead of some fossilized version of the software that should never be used for security or incompatibility reasons.
The above also applies to how generic computers should work, I understand that Apple devices are fairly close to this obvious process but I believe (offhand) that they lack end-user empowerment / management of authorized authorities at a bios level.