So, I see three things that seem to be of primary concern where preboot video screens are wanted by most users.
1 - BootPicker
2 - Verbose boot output for troubleshooting
3 - FileVault access...
For my part, BootPicker has become unnecessary. If Windows is your concern, we can now apply a newer bootcamp driver in windows, and select out APFS / HFS+ drives for booting back to macOS, and it works very well for me. I haven’t investigated Linux installs yet, but I have a pretty good idea how to make that work too.
Verbose output would be really useful. I needed it just this week in fact. I installed my old EFI card for that purpose. However, I believe that you can boot into verbose mode without EFI. You won’t see the screen output, but if booting is successful, the verbose output may be sent to the BOOTLOG file contained in the EFI disk partition. I’m not certain on this, but I encourage others to investigate. I will do the same when time permits.
Boot Screen output won’t help much with FileVault right now since it’s disabled in Mojave w/cMP, perhaps Apple will do something here. To me, this is the most valid request.
Just my 2¢