OVMF includes its own implementation of the VGA BIOS which must be used together with the BIOS image. So the override of the VGA BIOS path is quite deliberate; there doesn't seem to be a way to point at an arbitrary VGA BIOS file with libvirt. The override of the keymaps path is less deliberate, but would be addressed by a symlink in the ovmf package.
OVMF includes its own implementation of the VGA BIOS which must be used together with the BIOS image. So the override of the VGA BIOS path is quite deliberate; there doesn't seem to be a way to point at an arbitrary VGA BIOS file with libvirt. The override of the keymaps path is less deliberate, but would be addressed by a symlink in the ovmf package.