Gestalt D&D 5.5e

Gestalt D&D 5.5e adds support for Gestalt characters to the dnd5e system: play two classes at once and gain the features of both, without your effective level, proficiency bonus, or spell slots scaling as if the two classes' levels were added together. A Bard 5 / Paladin 5 gestalt character has the features of a level 5 Bard and a level 5 Paladin, but is treated as a level 5 character overall — not a level 10 multiclass character.

Gestalt replaces dnd5e's standard multiclassing rules for that character; it isn't layered on top of them. With it enabled on a character:

• Effective level, proficiency bonus, tier, and HP all follow the base class ("Original Class") instead of the sum of every class.
• Hit points use whichever single class currently grants the most, rather than adding both together.
• Saving throws, skills, and weapon/armor proficiencies come from every class, not just whichever one dnd5e considers "original."
• Ability Score Improvements are checked for overlap between classes, with a warning (never a block) if a secondary class's ASI is redundant with one the base class already grants — toggleable table-wide.
• An optional toggle doubles leveled (non-Pact) spell slot totals, as a simple stand-in for two separate spellcasting pools.

Requires the libWrapper module. Built and tested around using only two classes; see the README for known limitations and full details.