Magic Homebrew

Okay then, I am going to be running a
Hey, I've got 3-4 RL players and I'm aiming for 6-12 here. Of course its going to be more fatal here!
less fatal version of my Trapped in Time for nWoD. I was planning on running a fantasy style game with magic, but I don't own Mage: the Awakening, so here's what I've got for a homebrew so far. My biggest concern is making the mage OP.

Homebrew Sheets:

  • Computer is replaced with Knowledge
  • Science is replaced with Spellcraft
  • Occult is replaced with Arcana
  • Drive is replaced with Ride

Homebrew Rules:
  • Casting magic takes Willpower. A level 1 or 2 spell costs 1 point, a level 3 or 4 spell costs 2 points, and a 5th level spell costs 3 points.
  • Magic takes Level x 2 turns to focus and cast. Ex. A level 3 spell takes 6 rounds to cast.
  • The Meditate Merit has been increased from * to ***.
  • A character with access to spell can meditate for an hour per Willpower point to regain lost points. With the Meditative Mind merit, this is reduced to 45 minutes per point.
  • When casting, you lose any Defense that you naturally have (cover, armor, etc. still apply). If you are in anyway disrupted you must make a Resolve + Composure check to continue. You need one success per spell level to continue.
  • You can put an extra two dots into Eidetic Memory to be able to continue a spell with breaks. You can stop and continue the spell at any time, but if you begin a new spell, you lose the other spell.
  • The Black Magic (* to *****) and the White Magic (* to *****) merits have been added. Each dot grants three new spells at the next level. Specifics to come. As usual, the 5th dot costs double.
  • Magic(al damage) is determined by a Spellcraft + Intelligence check. Magic deals aggravated damage unless otherwise stated.
  • Using a magical item requires an Arcana + Wits check.
  • A spellcaster gets a penalty for any speed penalty she incurs from armor.
  • The Arcane Focus merit (* to *****) has been added. You can have a item that serves as an arcane focus. As long as you have this item and use it to help in the spellcasting, you get a bonus equal to the amount of dot spent in the merit. Ex. Two dots will give you a focus that grants a +2 to magic checks.
  • Arcane Resistance (***) merit has been added. You can replace your Defense (lowest of Dex or Wits) with your Arcana skill if you are fully aware of a spell that is about to be cast at you.
  • Each player gets 35 xp to start the game, as they are all "seasoned" adventurers.