Though coding will be hard, I think it'll be bearable. The good thing is that most of the game is just based on card values.
Over time, I'd developed two different games.
Their objective is similar. Both players represent an Incident, and you want the opponent's Incident value to hit 0. You draw characters who fight each other. Defeating a character makes the opponent's Incident value go down by said character's Influence value.
The complicated version :
There are two types of fights - Nonspells and spells. Nonspells only require a character to attack. Spells require a spell card, whose attributes (like demon, spirit, etc) must be fulfilled by the player's party.
Values necessary for battle include HIT (hitrate), EVA (evasion rate), and POW, which determines how much LIFE is lost if the attack succeeds. The character isn't defeated and the Incident value doesn't go down until LIFE hits 0.
These values can also change depending on what row the character is in. The front row is "focused," and the back is "unfocused." (Think about how the row might affect values for Meiling or Patchouli)
Other things include battlefields, which determine how many character slots are in your rows, and how much SP (spirit) you regenerate after a turn. Spirit is used to do things from playing characters and spell cards to using a character's special ability.
Many characters, while in play, affect stats all over the playing field. While in play, Reimu might lower the EVA of all opposing demon-type characters, while Youmu might increase the EVA of all her allies. Along with battlefields and items, much of the game revolves around building up stats before finally attacking.
The simple version :
Characters have POW and EVA. Battle is very much like a tug-of-war. Players take turn boosting their character's POW with spell cards. At the end of the battle, whoever has the highest POW wins. EVA values prevent the opponent from boosting their character with low HIT-value spell cards, limiting their options. Spell cards must also match the character's attributes.
Many characters still provide stat changes to others while in play. SP still exists, but is much more forgiving.
Actually, the game can be further simplified, but that probably won't make it more than a minigame.
Which, actually, since I have such little programming knowledge, might not be a bad idea.