I didn't think about this.
Though since I barely know Javascript basics, I have better chances with
adding to or tweaking Launchy's sources than with working on a whole new idea
(much harder to implement for me).
On the other hand, even in doing this, I would need to know the basics of
extensions creation. So in the end, you're right anyway.
Btw, it seems that for Mozilla, "addon" is a generic term encompassing
themes, extensions and plugins (like a flash plugin, GNU forbid).
I'm specially interested in making this work because it would save a
select-copy-open_CLI-write_you+TAB-paste-enter, and repeat on the next video.
But most of all because without Javascript (NoScript extension running for
most of my browsing, so no html5), I have Unplug that works quite often, but
youtube-dl works nearly all the time. So it's like the lowest, most basic
tool that works in the worst conditions (no Js).
About cli apps, I wonder if they are as safe as a fully equipped browser.