Hey, I just found the support threads for hopefuls. I thought I might as well chip in my view on how one of my favorite characters might play. Rather than Psynergy, I thought to focus on a Djinn build.
Specials:
Forward B: Venus Djinn. Unleashes a random Venus Djinn to attack. Includes Geode, Flint, Echo, Sap, Steel, and Bane.
These focus on forward attacks that deal damage. The Djinn is summoned above and before Isaac, and swings down with his blade for the strike. The Djinn summoned will determine slight additional effects, such as mild poison or HP recovery, or just more damage.
Down B: Mars Djinn. Unleashes a random Mars Djinn to attack. Includes Fever, Scorch, Torch, Char, Shine, and Fury.
These focus on AOE fire attacks around Isaac. Which Djinn is summoned determines some minor effects, with Shine giving a similar debuff to the traditional flower rod hits, maybe some other minor harassment.
Up B: Jupiter Djinn. Unleashes a random Jupiter Djinn to recover. These include Kite, Gasp, Waft, Whorl, Lull, and Zephyr.
These are recovery moves, with the Djinn blowing Isaac up. Aesthetics may change (I imagine Kite may give him an extra jump), but recovery amount should be near identical.
Neutral B: Summon. Summons Djinn back to Isaac. Power of move depends on number of unleashed Djinn.
Essentially, this Isaac would play as a rotation. You would unleash Djinn with each move. Each time you use a special, the Djinn unleashed becomes unavailable, until eventually you can't perform that special anymore. You see the Djinn floating as little colored dots around Isaac, with color matching the element.
As you unleash more and more Djinn, Isaac's attacks become weaker, and he becomes lighter.
However, when you use Summon, the number of Djinn you have on standby translate into a summon that does extensive damage and restores Isaac's strength. The AOE, exact effect of the summon, etcetera, are all controlled by how many Djinn he has on standby, as summons were managed in Golden Sun. So, while dropping all your Djinn is incredibly risky, since you become one of the weakest and lightest members of the cast, it lets you unleash an incredibly powerful summon.
Unfortunately, Mercury Djinn are left out, but their theme is healing anyway, so it's harder to work them in well.
Thoughts?