ASW – Alternative hero leveling.

If the perk grants a necessary spell at a decent level, there's no need to invest in the same school.

So, I understand correctly that you intend to shift the perk to Light? If so, then the question of the Shield school is resolved (after all, this is about character progression, not magic).

With their high magic, Summoning is a perfect fit. But aesthetically, Dark is needed for the Elves instead of Summoning, and Summoning instead of Chaos for the Dwarves. But for the Dwarves, this would destroy one of the amazing Chaos progression paths. And the Elves would end up looking like the Inferno faction.

In Warlords, Dark for the Warlock and Summoning for the Elf look great, but there are also many changes to the spells. So, the question comes down to the spells. It is quite possible to make Dark advantageous for the Warlock. However, this is already a topic for a separate project.

The fact that the Elves will become "similar" to the Demons is not an argument. Demons have a lot of mana and little Special Points (SP), while the Elves have the opposite. And all the consequences that come with it. In addition, it will not be possible to avoid repeating schools: with 7 races, there are 6 combinations. In the original game, the Dwarf repeats the Elf.
Another thing is that if you give the Elves Dark + Chaos, then Chaos + Summoning must be given to someone else. The first candidate is the Mages (and they don't need Light anyway, as mini-artifacts already enhance them). Accordingly, Light + Summoning is freed up from the Mages and goes to the Elves, or to the Dwarves. However, in both cases, there is a "BUT": Enchanted Arrow and Gnomageddon (both require Chaos).

For now, these are just ideas. A total of 3 changes, but Dark remains in its place.

Another possible candidate for Chaos + Summoning is the Demons. This was tried in Warlords, but it turned out to be unsuccessful (they switched to the first option).

There is an idea for the Elf: make Summoning their native school instead of Chaos, and get the necessary Chaos spells from progression (put them in the Elven schools). Or even simpler: give Chaos spells to heroes at the start. That is, in fact, play with 3 native schools (but without progression in Chaos).

You can also try the "Chaos + Summoning" option for the Elf. And get Light from Defense and Offense (the main thing the Elf needs is Haste). But there is a "BUT": Light Unicorns.

They are both pure passive skills and not antimagic.

This is the only thing they have in common. But the goal of your project was to move away from upgrading useless perks for the sake of useful ones. So, I think "Resistance" is useless if I want to go into "Evasion" (the perks solve fundamentally different tasks).