TBH, the first Persona you get should depend on a beginning questionnaire. Like in the Fallout series where questions determine your beginning stats. This way you can still be the "Wild Card" while having a deeper personal attachment to the MC (which is a persona of the player). Actually I'm surprised they haven't done this.
In fact I'm of the opinion that your first Persona should also hold massive potential should you choose to stick with it. What I mean is that there could be an additional fusing option: Reinforcement. This is where you can fuse another persona of certain strength or level and carry over skills and stat boosts to an existing persona. This doesn't even have to apply strictly to the original persona. Each new fusion should have a potential. Ultimate personas have very little in the way of it. They have already achieved their maximum potential through fusion. Certain arcanas would have better potential than others, or side effects based off their personalities (like the Fortune arcana getting random stat growth through reinforcement).
Check my FictionPress: http://www.fictionpress.com/u/882728/ I love Rias Gremory.