I added something like this to my (very) pink mohawk game. Here is the text of what I added:
[ Spoiler ]
*Empower Spell [Spell Category]*
The Empower Spell ability allows an Initiate to boost the power of spells she casts by increasing the drain and sometimes adding to the casting time.
The Empower Spell Metamagical ability allows the initiate to add up to her Initiate Grade to the effective force of a spell, this also adds two times that amount to the Drain Value of the spell. This does not increase the force, but it does increase the effective force. So a force 6 spell cast by a Grade 4 Initiate will still be limited to 6 hits on the casting test, however it will act to the target as though the force was a maximum of 10. For each complex action spent preparing the spell reduce the drain value by 2 to a minimum of the original drain, this ability will not allow the spell drain to go below its normal value.
Using this ability is very obvious to all around you; it makes the caster crackle with mystic energy that is both visible and audible. As soon as she starts casting using this ability the caster begins to crackle with the energies, so taking the time to reduce the drain can be quite dangerous.
Any effect that is influenced by Force is affected by this ability. Empower Spell comes in five types and can be purchased multiple times. On each Initiation the spell caster can acquire a different spell category. There is an Empower Spell for Combat, Detection, Health, Manipulation, and Illusion.
Examples:
Blaster the Grade 4 Initiate Mage is casting a Mana Bolt on Slash the Samurai. Blaster has a Spell Casting of 6 and a Magic Attribute of 9. Slash has a Willpower of 4.
Blaster decides to Empower his Force 6 Mana Bolt with the full 4 points, so he rolls 15 spell casting dice (9 Magic + 6 Spell Casting) and scores 7 hits. Since the spells Force is 6 only 6 of the 7 hits count on this test. Slash rolls his 4 willpower dice and scores well with 3 hits. So Slash takes 13 boxes of physical damage, 6 from Force 4 from Empowerment and 3 from Net Hits.
Now Blaster has to resist the drain of the spell. The normal DV for a Mana Bolt is F/2, however because Blaster Empowered the spell and didn’t take extra time to channel the energies he’s resisting 3 (Force 6 divided by 2) plus 8 due to the Empower ability for a total of 11S Drain. The Drain is still stun because the base Force was below his Magic Attribute.
If Blaster was able to take 2 complex actions to channel the energies of the spell his drain DV would have been 7S, base drain of 3 plus 8 from Empower minus 4 due to channeling for 2 actions.
*Edit
I would not recommend something like this for any normal game.
-D