I’ve tried climbing this mountain before, and I wish you luck. Here are a few of my notes, in case any of it is of use. This was meant to be a reproduction of the Mage:The Awakening spellcrafting system ported into the One Roll Engine by Greg Stolze:

Improvised Spellcasting

Creatively combine effects from your arcana and extra Spell Parameters for things like range, duration, and area of effect, until you’ve described exactly what your spell does. Each additional type of magic causes -1d to your dice pool.

Improvised castings are instantaneous, and involve a single roll. Combining Gnosis+Arcana (Use the highest Arcana that is part of this spell).

+1d for having a focus devoted to that arcana
+1d for spending mana (up to 1)
+1d for spending willpower (also 1 max)
+1d if the spell coincides with your Vision, Belief, or Passion (These replaced Mission, Duty, and Craving in my homebrew)

Extended castings are a higher investment, but higher payoff. It requires some kind of sacrifice - a significant object or a living creature. Each roll takes ten minutes*. To successfully cast the spell, a difficulty (1-10) and a needed number of successes (1-10) is set by the GM. I ran this as arbitrary, but feel free to have your own difficulty levels. For each interval of extended casting, you must spend willpower to continue attempting the spell.

+1d for a ritual with hour-long intervals
+1d if your ritual involves several days prep time and/or significant materials costs
+1d if the spell coincides with your Vision, Belief, or Passion (up to +3d)

Improvised Spell Parameters

Long Distance Magic (Requires Space 2) For targets out of view. These spells require some object with a connection to the target. The penalty is based on the strength of its metaphorical connection, not the distance to the target.

Intimate -1d Familiar -2d Acquainted -3d Vague -4d Tenuous -5d

Multiple Targets Hits extra targets at full strength; The spell can now be Dodged, however.

Two -1d Four -2d Eight -3d… (Round up to nearest double)

Area The standard spell takes effect over a flat 1 yard radius. Double the penalty for the same cubic area. 2 yard radius -1d 4 yard radius -2d… (Et cetera, round up to nearest double)

Duration The effect maintains over Width or Height in the relevant time scale, per GM. Some effects might not be able to extend over time, or extend differently.

Minutes -1d Hours -2d Days -3d Years -4d Forever -5d

Misc Spell Modifiers Pick one per extra Mana spent, up to three.

Casts in Minutes +2d Casts in Hours +3d Causes 1S to caster’s entire body +1d

Repeats Effect Next Round -2d Must be cast after success with an other skill +1d

Difficult (-2d) to Counterspell -2d

Ignores X armor -2X Can be blocked by armor +1d

Spell effect covers a ~150 ft radius -3d

Summons one Threat 2 Creature -1d

Spell requires unusually complex ingredients and preparation +2d