I’ve thought about this since I first found the 4e multiclassing feats — and when optional “character theme” rules were introduced with Dark Sun — and finally when hybrid classes were introduced with the 4e Player’s Handbook 3.

4e multiclassing kind of sucks — but it also better than 3e multiclassing. The multiclassing rules in 3e are a lot like the CR and Template system in a “we don’t know how this works, but here’s one of the tools we use” kind of way.

I think the “answer” to multiclassing problems which have — and let’s be honest — basically always existed, is making an individual character feel like they are somehow “mostly one thing, but also partly another thing.”

Players figured out how to cherry-pick the best class features and that borked 3e multiclassing, but 4e presented multiple systems which — if taken together — should really have resulted in the kind of multiclassing “we always wanted.”

They’re just spread out across multiple disparate systems.

Feat-based multiclassing ultimately failed because of a problem identified as the “Feat Tax.” Attack and Defense score advancement through the levels forced PCs to take certain feats or suffer in combat. These were the basic “Expertise” and “Superior Defense” feats. Feats went back to “patches on a broken system.”

The hybrid class system ultimately failed because — leaving its complexity aside — 4e classes are so front-loaded with inter-dependent features and powers that it’s easier to build an entirely new class from the ground up with all the stuff a player wants than to build a proper hybrid class.

Character themes on the other hand, are easily implemented but lack variety and… well, let’s just say that most of them suck.

But! If these things were all combined, a solution may be reached.

Part of the problem with hybrids and feat-based multiclassing was that whatever secondary class was chosen had to jive with the character’s ability scores. If you only had one good score, you had to choose another class with the same score.

If your character was Wisdom-based, you won because 4e is incredibly lopsided in favoring the Wisdom score for character classes. Divine and Primal classes occupy two out of the four primary power sources — Arcane, Divine, Martial, and Primal — and occupy the “secondary ability” slot of many Arcane and Martial classes.

Themes introduced the idea of theme powers using the character’s highest ability score instead of choosing one ahead of time. This was a brilliant solution to open up themes for everyone — but less than half of themes follow this guideline.

So here’s the answer — character themes become “dual-classing,” and follow the basic rules of feat-based multiclassing with the following change: instead of using a power-replacement system, the dual-classed PC gains new powers at the regular theme intervals, however with powered “marked down” in usage.

At-will powers taken from the secondary class become encounter powers. Encounter powers become daily powers. Daily powers are out of the question. Basic secondary class features can be gained at 5th and 10th level, per normal.

This is balanced by the “cost” of making these secondary powers use the PC’s primary ability score — which can be completely different from the original.

In other words, a Strength-based Martial PC such as a Fighter or Thief can dual-class as a Wizard and use Strength for his Burning Hands spell, which is then “downgraded” from an Encounter to a Daily power as a result.