It have only 100 active installs and have no analog. I think you can write the same thing, improve and populate it. For example there are no way to get $_FILES var via sending form in case of use this lib.
No, not for only that reason. This is global custom class, that covers wp_ajax at all and simplify it, like your metabox class simplify classic way to make metaboxes. The lib, that I give you a link is unique, but nobody knows about this lib. Just test it and I wish it will inspire you to make more better ajax class and maybe create another metabox.io-sized project 😉
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