This is a use-case and approach covering commercial off-the-shelf motherboards sold in bulk to a small set of customers (per board) whose OS selection is part of the customer requirements, as opposed to individual end-user sales where any OS might be used.
While a perfect candidate for LinuxBIOS technically, not having a traditional BIOS would leave a bad first impression as the customer immediately believes they need to perform additional work to integrate the product with their solution.
The solution is to provide a "normal" BIOS menu that provides common BIOS functions and can boot from install media, allow an OS to be installed with its standard installer, and then boot the OS from the installed media.
The trick is to make this all seamless.
Only market leading modern OSs need be supported by default:
First: Linux 2.6-based GNU/Linux
Second: Windows XP, Windows Server 2003, Windows Vista
Since Linux can already boot as a payload directly, "all" that is necessary is to make it appear that install media and the OS are booting from their selected devices as if using their installed bootloaders (Grub, ISOLINUX, SYSLINUX).
Windows requires additional features such as BIOS interrupts, ACPI, SMBIOS, etc. In particular, the following standards need to be supported:
Interrupts are supported through ADLO. The others ???.