Magic system sketch v2

After all this time, I've still haven't found a magic system that I like 100%. This is the current iteration I am working now. Numbers are made to fit with this other previous work, though they can work with any rules using roll-under, under a magic stat such as wisdom or intelligence.

Wizards grow in 2 fields:

# of Spells and Magical skill

There is a magic skill, lets say X in 6, that grows as the wizard gets more powerful. 

Using certain magic items (like oracles) passive reactions (like detect magic) or small magic effects (cantrips) uses a roll of this to work. Wands also use this as primary factor of power, I will explain soon. 

# of Spells is very reduced, even though if spells themselves are more "versatile" and should not have a single, ultra-specific effect.I want to limit it to four or five even in very powerful wizards. More spectrum is added by gathering items (jewels, wands, etc) that allow casters to have more repertoire. This magic items are not too overpowered because they need a good magic skill score to work, so it is fine. It is hinted in the books that Gandalf uses fire thanks to the elven ring he carries; so wizards having lots of power and not many spells has basis on the holy fantasy books.

This is a hint on how this could work:

Lets say you have a spell list of 2: Heal and Cold

You use the Cold spell to deal damage, so you roll 1d6 and check your magic score (3)

If you roll under or equal your score, you take that number of HD from your enemy or enemies (you decide how this damage is divided). Lets say that the Cold spell has a side effect or alternate effect of slowing enemies down: then everyone affected rolls a save or is paralyzed. At 0 HD they are frozen permanently until defrosted. 

Having more level or good gear might increase the number of dice you roll: If you roll multiple d6, treat them separatelly

If you roll OVER your magic score, then the result is assumed to be equal to your magic score (3) but either the spell is lost if all dice are over (like a vancian system) or you lose magic die which roll over (making energy decrease instead, instead of making spells deplete separatelly)

Depending on the spell, the number rolled can be interpreted as HD of damage, yards, meters, possible individual targets or just an abstract degree of effect (up to the GM to decide the spectrum of effects on all results from 1 to 6). 

A very interesting interpretation could be to make a spell (for example, CHARM) be able to target a monster with HD equal to [number rolled + wizard HD]. So the spell always works with monsters under the wizard's HD, and makes a nice progression for spells to grow up in power as the wizard does (per BX rules, sleep, charm or hold person have hard caps on which monsters can be affected based on HD or size, but seem a little arbitrary and make you wonder: why is a dragon never affected by a sleep spell, EVER, no matter the wizard's skill? it seems something that could happen on a fairy tale. Why not in a D&D game?

So, wizards get exponentially better as they raise their magic score, which is something I activelly want. My idea is to make multiclassing possible, but mathematically sub-par. Having one fighter and one wizard should render more "powerful" characters than having two fighting-wizards, even if the latter might be useful in some situations. 

Having made this, only one more task remains: to make a provisional spell list to be tested, and deciding what kind of effects can be used as cantrips or produced on a different way.

One idea is that both HEAL and COLD, as do FIRE or BOLT, can produce light under certain conditions (for example, when used by a "magic score=3" wizard who is carrying a wand). This way, you can have spells produce lights of different colors depending on the wizard's favored powers (just like jedis have different lightsabers)

Another one is that spells give you both active and passive abilities.

Having mastered the HEAL spell means that you must be a very lawful or righteous person, so you have a +1 to turn undead.

Having mastered the COLD spell might give you a passive resistance to cold temperatures, and so on. 

Ah! I almost forgot: Wands allow certain effects (such as light) but magically imbued wands give you an extra d6 when rolling to their favored spells (Wand of cold gives you an extra 1d6 when casting cold, for example). This die never depletes unless you are one of those sick people who makes wands a depleting resource.

Here is a big good list of spells alongside the cantrips/passive bonuses they grant to the caster that memorizes them. While I make my own list (the real tough work) this can serve as inspiration