I would love this as an option as well. I constantly copy and paste from IDEs and it removes all the indentation and adds extra new lines. Having to constantly remember to press shift every time I want to paste is very annoying in what I consider to be a plain text editor.
Being able to rebind paste and paste as plain text would also be a great option.
There is already an option: Settings > Editor > Convert pasted HTML to Markdown. The downside is that it doesn’t let you use Shift when you want to paste formatting.