What remains here is to decide on how Winning and Gaining interacts with Magic.
The most straight-forward implementation is of course: if you use magic to deal more damage to X than you suffer yourself then you gain Winning and Gaining on X.
But what would it mean to "gain" or push someone using magic? (Plus, only looking at damage feels reductive and Fantasy Battle like. I ideally would like lots of kinds of magic to count towards winning and gaining on another mage, not just simple zap spells)
What I'm fishing after is, if there could be a better way to implement "magic duels" than the dull C7 implementation with free counterspelling (what the rules call dispelling). And then tie Winning and Gaining to that.
For instance, as soon as a spellcaster is "gathering the winds", that is taking either the Cast Spell action or the Channelling action, you can (or must†) contest that. Make a Channelling Test yourself, and resolve an Opposed Test. Your SLs against the other caster's SLs.
†) as you will see below, the Channelling action is redefined to include a "steal the winds" aspect. So while you could skip this opposed test if someone is "only" casting a spell, if you don't oppose a Channelling attempt, that means forfeiting in the same manner as if someone is waving an axe in your face and you don't even try to parry it. (Away from rulebook at this moment, but I seem to remember some rule or rule discussion that covers what happens when your opposed test isn't opposed)
The difference in SLs sets the stage for the impending battle. Possible mechanical implications:
* Having you enjoy the SL difference in actual spellcasting (if you won by 2, you get +2 SL and he gets -2 SLs) is probably too strong
* You could get a discount in Magic Points. This has the advantage of not actually impacting your actual casting tests, but instead draining your Magic Points if you're on the losing end of the duel. It also has the dis
advantage of not impacting your casting, since this probably mostly impacts how many Magic Points you have left after the duel.
* Having the duel instead impact the number of magic points you can spend is both more and less impacting. More in that your ability to cast bigger spell is affected. Less in that you don't actually lose any MPs. If your Will Power Bonus is 5, and you lost the duel opposed roll by 2, that means you can only spend 3 Magic Points a round, while your opponent can now spend 7 (assuming he had the same WP score). I'm not sure I like the latter possibility. Getting to use up to 4 MPs feels fair since these spells doesn't really do much more than regular 0 CN zap spells. Getting to cast 7 CN or 9 CN spells at no penalty is much more of a game-ender, I think. Perhaps you have more experience casting these big boys?
I'm torn between these latter two options. Possibly even
* if you lose the duel, this lowers the number of magic points you can
spend. Example: you can now spend only 3 MPs instead of 5 per round.
* if you win the duel, you instead get a rebate on the magic points you do
spend. Example: when you spend your maximum of 5 MPs it actually only costs you 3 MPs.
This way I get to both eat the cake and still have it. Cakeism at its best
What to do if you feel you're losing the duel? That is, if you don't like the penalties for losing (as discussed just previously)
Why, spend your action to Channel of course, to wrestle yourself out of the hole you're put in.
Any channeling attempt not only amasses magical energy per the original rules (which we now can express as "you're gathering temporary Magic Points that can be used for your next casting only"), it also forces a new Opposed Test
where you can reverse the fortunes if you rolled badly the last time.
The cost, of course, is that you aren't casting a spell this round.
The opponent does a (free) Casting Test, and you compare SLs just like before. From this moment on it is the new result that applies and not the old one.