One critical table for each type of weapon sounds reasonable.
Short blades, long blades, ...
Maybe short single edged blades, short double edged blades, long s.e. blades, long d.e. blades, ...
Something along those lines?
The damage doesn't have to be 100% unique. Some crits can be made with a broad sword as well as a dagger, but some should be unique to the weapon type.