I suggested directional shield blocks in warband beta. Taleworlds did not like it.
I doubt that what the OP suggests can be implemented within the module system.
That's too bad; I'd really prefer directional shield blocking. It would kind of suck though, unless the shield counted as a solid physical object against melee weapons. That way, blocking to the left with a large shield would also somewhat block overheads and thrusts, but be vulnerable to attack coming from the right.
Even better would be if the non-blocking shield animation had the arm raised up a bit, so that attacks would still be blocked when "dropping" the shield. Back peddling speed would need to be reduced as well.