I don't dislike the idea but it'd need more work graphically. Like this it's barely visible. Making it obvious to the user that this part of the screen is there for your to click on should be priority #1 when you design a nonstandard checkbox.

Edit: And remember, something doesn't necessarily have to be a checkbox for you to select it, it can just be a bevel of some kind. You don't even have to require clicking as an action: You can square-select items (like you would in a file manager), you can long-press (like you would on mobile) etc.

It's possible my monitor brightness is wrong (nevermind, you're right, I see it now), and thanks for the feedback and sharing tips.