I feel like most people using bootstrap don't really care about supporting IE 6-7. If you're really serious about supporting these browser there are two main reasons :

- you want people from the companies who are forcing them to use IE, to be able to view the website as intended (and I'm sure they can understand that it doesn't look as good as on the latest version of Firefox)

- you want people in China to have the best experience on your website.

Then I believe you should look at other solutions.