I like the idea of Variant Multiclassing, but it doesn't hit all the notes I'd like, plus leaves some discord and disconnect on how useful some of those abilities actually are. So I'm looking to try to do something similar, but different. Let me know what you think.
Gestalt Training (General)
You are trained in the abilities of others. While you may not perfect a single aspect of yourself, you can instead become more versatile.
Benefits: Choose a class you do not have levels in. You gain a single level of that class. You gain all of that class's Class Features, including such as spellcasting, smite evil, wild shape, etc., available to a member of that class of a level equal to the number of times you have selected that class with this feat. You do not gain the hit die of that class, nor class skills or skill ranks per level of that class, the base attack bonus or the saving throw bonuses of that class, nor the weapon and armor proficiencies of that class, though you gain all other aspects. You count as a member of that class of a level equal to the number of times you have selected this class with this feat and must follow any traditions or codes normally placed upon members of that class, such as a Paladin's requirement to be Lawful Good or a Druid's inability to wear metal armor.
At 20th level, if you have selected this feat 10 times and selected the same class all 10 times, you may select the saving throw bonuses, base attack bonus, and hit die of a 20th level character of the class selected with these feats if those bonuses are better than your current bonuses.
Special: You may select this feat multiple times. Each time you select this feat, you must choose to either add a level of a class previously selected with this feat or select a new class. This feat stacks with itself, adding levels of a single or multiple classes to your character.
You may only select this feat with the feats granted to all characters that advance through class levels. This feat may not be purchased with the feats gained through racial hit dice.