Combat in the computer game is always a simplification. You can't have anywhere near realistic combat because you are using fingertips on keys and hand on a mouse to make combat moves as opposed to all parts and muscles of your body. And picture you see is 2D instead of a 3D, which means that your eyes can't determine distances as well as in the real life.
It also have to be simple enough for a new player to be reasonably effective. You can't force player to train combat for years to be able to play the game.
MB combat system is the best computer game combat around because it allows fluid combat against multiple enemies using wide variety of the weapons.
As Viking Conquest have shown, spear can be effective in the MB combat system, you don't have to change it. I did not see changes VC did to spears, but I suspect that the trick is in changing how damage is distributed through the trust. Trusts shouldn't be as sensitive to "effective distance" then swings are, because trust does not rely as much on momentum of the weapon as a swing. In other words, problem is that spear trusts in BL deal too little damage when they are not at the optimal reach of the weapon.
Still, spear combat in BL is much better then it was in the Warband.