I don't think it's a problem if it follows common sense and is somehow generous. It could actually give an interesting gameplay balance to different weapons, like bladed weapons being more affected by armor, but being able to block more than non-bladed weapons, and smaller weapons being faster but being weaker on block.Having a maximum amount of damage a weapon can block would bring some issues, like the player not being able to determine if they can block the incoming attack or not, thus turning it into a gamble, which is undesirable.
However, not being able to block with a dagger as much or as well as with other, let`s say more conventional weapons, makes sense, we`ll bring this up.
The amount of damage blocked could be a base statistic of the weapon (calculated from weight, size and balance, just like the other values are calculated during blacksmithing), and would be increased by the skill in the weapon category, control and strength (with the final total being shown on the character sheet). I don't see how it's more of a gamble than the crush-through, which is already implemented while being weirder, much more obscure and less universal.
At least this mechanism would work for everything and would be easily exposed to the player, while being easily understandable.