Like the idea, but I prefer them being passive traits.
Granted we don't know what the 300+ list contains but it'll be nice to have...
[Self multilation Achievements]
"Shot through the heart" achievement - For receiving 9999+ damage.
(Means you went somewhere you are not supposed to

)
-> Gives 1% damage reduction vs critical hits (because you are now paranoid so you wear an extra metal plate near your heart)
"Hades' Favored I/II/III/IV..." - For being KO-ed X-times
-> Slight reduction of down time for being KO-ed (because of been that done that)
[Mob killing Achievements]
"Sheep Shearer" - For killing 1000 Karakuls
-> Allows sheep mobs to drop 1 extra item (because practice makes perfect)
"Snurble De-Tufter" - For murdering 1000 Snurbles.
-> Allows snurbles to drop more tufts (because practice makes perfect)
[Being lucky Achievements]
"Luck of Legends" - For making a 5-materia item.
-> +1% chance when making Forbidden Materia melds (because you are just that god-damn lucky)
"Tiffany" (or any other famous brands) - For making 100 HQ GSM item from NQ items
-> +1% chance of getting HQs from NQs (because you are that gifted craftsman)
-> Similar achievements for every craft.
[Finishing Move Achievements]
"Burnt to a crisp" - Killing 1000 mobs with Flare (+1% damage to Flare)
"Slow over a stove" - Killing 1000 mobs with Burn (+1% damage to Dot effect)
"BBQ Skewerer" - Killing 200 mobs, 5 at a time with Skewer (+1% to ATK Bonus from multiple mobs)
etc etc etc