• This is not a v0.x issue.
• I have searched the issues of this repository and believe that this is not a duplicate.

Expected Behavior 🤔

I would love the ability to use a variant with any string and with that variant I could style the component using theme overrides. For example, let's say I have 4 types of buttons throughout my app and each button has a custom variant, inside theme I would simply use MuiButton with my custom variant names and style them as I please. The variant would act as an identifier and would give the theme more flexibility in styling the entire app and it would not tie me down to a preset list of variants.

Current Behavior 😯

Currently variants are limited and come with additional styling.

Context 🔦

Limits my ability to use theme to a greater extent and pushes me to style more locally than globally.