I've got an idea. Hear me out.
Let's go with a structure of magic and power scaling to 3E, perhaps knocking off some of the worst saving throw scaling thanks to Next flatter numbers. Also, take advantage of the Next reported intention to have individual spell power scale by the slot it is cast from, rather than the level of the caster. Then add in a spell called "counter magic," which can work in any spell slot. Actually, add one version of the spell for each major group, "counter arcane," "counter divine," etc.
Set counter magic spells up so that they make it possible for a spell to have some weak effects through one, but not very efficient. When, for example, a wizards casts a counter arcane spell on his party, their saving throws go through the roof, and they get things like 3E evasion even on missed saves. Maybe they also get advantage on any saving throw versus SoD effects. So when the effect is up, it's hard to hurt a party with that kind of magic, and same for monsters.
Next, set up monster organizations so that about 75% of monsters either have counter magic casters of their own, or some supernatural/special abilities that work similarly. You could tie things like the beholders anti-magic in here.
Finally, the cherry on top, the wizard gets a several times per day ability analogous to turn undead, but for unravelling opposing counter-magic. Some of the more arcane monsters also have this ability, as does any monster arcane caster. Meanwhile, turn undead for the cleric can also be used to unravel divine counter magic. Or even better, instead of per day, make this a part of a skill, such as arcana.
There. Now the effective wizard can dedicate a big chunk of his spells to counter magic. Or he can get the party fried all those times they encounter arcane magic and he doesn't have the answer. It might take 1-3 spells per encounter plus an Unravel Magic use to keep the enemy wizards in their place. Meanwhile, the fighters and rogues on each side are going to town, trying to take out enemy spell casters when they can, to tip the balance.
I'm sure some people will complain that this uses up to much of the wizard's actions and spell slots, but I don't see what the big deal is. It's fine for the cleric to spend his spells healing. It's fine for the fighter to spend his hit points holding things off. What's sauce for the goose, is sauce for the gander. Don't tell me this wizard isn't twisting reality. All the wizards are twisting reality all the time, but the smart ones are spending some time trying to twist it back into something better for their side.
Maybe at really high levels the wizard will reach a point where he can shut down the opposition more easily. About the same time that clerics aren't heal bots, and fighters aren't bags of hit points.
