Adjustible spells are only available to Initiates. Once a character truly understands spell theory and can see that many spells are really the same spell with slight alterations it becomes possible for them to construct spells with some variable attributes. At the time of casting they can define which variables they will use and that will increase the drain based on their choices.
Adjustible spells replace several spells that are normally available. They cost double the normal cost of spells. If you have at least two of the spells that would be replaced you can replace them and get rid of all the spells that are no longer needed. This is designed to be used with the Thread Magic system.

Spirit Strike (Direct)
Type: M/P Duration: I Drain: F/2
This spell channels magic directly into the target. It can be set as a mana or physical spell. As a mana spell it can effect living beings or spirits and is resisted by will. As a physical spell it can effect living or nonliving targets and is resisted by body. Armor is bypassed.
Physical +1, Area Effect +2, Touch -2, Stun Only -1

Elemental Strike (Indirect)
Type: P Duration: I Drain: F/2
This spell hits the target with a physical force. Usually this will be mixed with at least one of the elemental threads. Each thread adds it's own special damage effects and +2 to the drain code. If no thread is used it will act as a telekinetic force instead. This is an indirect spell so apply half Impact armor to damage resistance tests.

Elemental Wall (Environmental, Area)
Type: P Duration: S Range: LOS (A) Drain: F/2 +2
This is the same as physical barrier pg 204. Elemental Threads can be added to this to cause damage to those touching it. This can further reduce visiblity through it.

Elemental Pool (Environmental, Area)
Type: P Duration: S Range: LOS(A) Drain: F/2 +2
This spell produces an area effect of the element on the ground in a radius of force in meters. The elemental effects may spread past this. This replaces ice sheet and similar.

Flight
Type: P Duration: S Range: Caster Only Drain: F/2
This is a faster version of the levitate spell but it only works on the caster. The base movement is (force + successes in meters/turn) x 2. For every +2 to the drain code you increase the multiplier by 1.
If you include the air thread then you can ignore problems from traveling fast and allow you to breath normally when you are going fast or are high up. I suppose you could include lighting or fire threads to look impressive.

Nice concept, and nice work - but I think you're moving beyond the scope of Shadowrun.

Well all the spells still fit within the paradigm, but I was trying to reflect a slow increase in the mana level.

This is the obvious extension of the tenancy towards making everything generic in a game system. I tend to think it's another step in the wrong direction - one of the basic flavor elements of the Shadowrun magic system has been the "learning specific spell formula" thing. It's bad enough that we don't have Mana Dart and Hellblast any more, no reason to make Stunbolt and Manabolt the same spell (even for initiates).