it works (except on the main page and some firefox pages)

It doesn't work most of the time, I wil keep using Ctrl+Tab and Ctrl+Shift+Tab

It's not a bad idea at all, it's got some problems though. It stops working in FF's website and preference tabs. Which in of itself is not a big deal. But it also doesn't work on youtube (probably because google has it's own shortcuts for 1 and 2). Unfortunately, that's a deal breaker for me because a third of my tabs are youtube.