Hi,
The problem with use of original ACPI tables is different resources which might be static in the tables. Like I/O ports (legacy, smbus, pmio etc etc) Plus there might be some regions of memory reserved, which are not on Coreboot etc.
Basically it is not so difficult to create your own ACPI tables.
Check this http://www.coreboot.org/ACPI_in_coreboot
I'm using my own ACPI tables and it works very well.
Rudolf