I wouldn't like Grim's hit average implemented, after all If we are going to be limited to one character (and I'm assuming we are) and weapons get tweaked on a regular basis, then these kinds of statistics are misleading at best. ((For instance what about those players that play light/small ships and help a team out by firing chain shot at an enemy's sails/rigging? By its very nature 70% of chain shot is going to be missing its target)).
As far as what data I would like to be tracked I would like more generalized data to be tracked. For instance:
Average play time per week
Average time zone played during
Average time spent PvP'ing
Average time spent PvE'ing
Total number of PvP instances fought in.
Total number of PvE instance fought in.
Time spent on the Open Sea/Distance Traveled
Financial stability of player (this one would be a bit hard to track, but i'm thinking along the eve online terms, does the guy use ships he can't afford to lose often and how quickly does it take him to recoup his losses?)
Etc.
This kind of data would give you a general idea of how skilled a player is in what areas of the game and whether he would be a good fit or a burden or liability to your guild.