I agree with Fraemi, on an open field with your mates running higgledy piggledy as they usually do, this would be useless.
I would enjoy seeing it implemented, however. Because some maps have close streets and narrow passes which could be effectively blocked by two or three pikes, leaving archers behind to shoot down the lane. Another place you could use it is siege mode, particularly if you make it effective against infantry in some way (just slowing down their movement would be enough, or even making it possible to jab the pike forward at infantry to resume normal fighting mode).
As for the shield bash, I loved that in single player, but in multiplayer I can see it getting old fast. Having a way to attack while still blocking the whole time would turn fights with shielders into boring slapfests until the shield broke. I do think it's worth a trial to see if it wrecks the game though (if you can test bumping the rider of the horse as well as the guy being bumped, then you can test this), particularly if it can't be used simultaneously with kicking.
-John
