One of the first things I noticed when I came to this page was the remark, "In fact, a BIOS which can boot from a 4K-sector drive is an exceedingly rare item - if, indeed, it exists at all."
I can't speak for any 'other' BIOS, but the 2nd Generation SAS products from LSI do have 4K sector support under INT13 Boot.
The only drawback to that support is the RMW (Read/Modify/Write) cycles that must take place in an environment that has no concept of 4K sectors.
The BIOS is smart enough to 'package' accesses and minimize reads in consecutive blocks, but of necessity is unable to do anything about the many one sector (512 byte) accesses.
On the other hand it does 'remember' previous reads into a 4K block, so that consecutive 512 byte accesses don't reread the 'same' 4K block when it hasn't changed. (Remember that INT13 is single threaded)
I don't know who this might help, but there it is!
P.S. I wish someone would update the DOS version of GDISK to work with 4K drives. Currently, it blows up when it sees one!