My biggest wish for this game:

Complex:

Total redesign of the SMN, to make it less 'generic MMO necromancer' and more Final Fantasy Summoner styled.

Step 1:

Convert ACN from being a damage type into a healer type. Give them leeches and Succor at early levels like CNJ gets. SCH becomes the natural job progression of the ACN.

Step 2:

SMN is now a Damage job based off of a healer class. Replace these little garbage pets with big powerful primal pets, but with a healing mechanic involved. The Primal spawns with 50% health, and that health drains away quickly. In order to keep the primal up and fighting, the SMN must constantly heal it to keep it's health from dropping to zero. At 0 HP, the pet despawns. On the other hand, the SMN must be careful not to overheal their pet. If the Primal ever reaches 100% health, it immediately stops and activates it's ultimate AOE attack, nuking everything in the area, then despawns. 90% of the SMN's damage now comes from their pet. SMN is no longer a DOT stacker, but does still have Bio and Ruin to throw around between healing their pet.