I'm not 100% sure if it's possible, but apparently, there are some AMD 15h(Mostly AGESA) boards than may be interesting to Libreboot:
*HP Pavilion m6 1035dx
*LENOVO G505S Is being already in progress
*MSI MS-7721(Hudson, FINTEK F71869AD super I/O)
*AMD DB-FS1r2 (Parmer) (Dev board for FS1r2 Socket, lots of laptops were based on that)
*AMD DB-FP2 (Thatcher)
I know it seems like a lot of work, but these look, again, promising and could give libreboot the boost it needs.