The people we are 'RPing' are experienced fighters. With high level characters with higher WPF autoblock just represents the ease with which a trained warrior would control their swords. Adding 4 attack and block directions for a swing would simply be a pain in the arse.
You really should try Two Worlds II if you haven't already.
Btw. about riding a bike argument, that shitty MMOTPS wannabe game called APB is controlled in a same way as most driving simulators. You can play them with W,A,S,D as well. However APB driving model is probably the worst I've ever had the pleasure to try. And similar game like GTA IV has quite decent driving model. You know why?
Because it has better physics model. No additional controls, just better physics. If you want additional controls you need to make your game for different controller, not for keyboard and mouse. Steering with mouse works well in L4S but in Warband you need free aim for weapons...
W,S,A,D is the best keyboard has to offer. Additional controls only complicate things. Work on physics model instead and things will be a lot more different, both for cav and inf.
Also fixed four attack and block directions aren't enough for me anymore. I want 360 degree combat