No no, you don't need to edit the meta files at all if you just want to add/remove extras for that specific time you're playing. For the forced light bar every time, I actually have never messed with the forced components, but I think your issue is this:
<requiredExtras /> EXTRA_2 </ requiredExtras>
Copy and paste the one I've put underneath, it should work. Yours also has some spaces between the words and tags, so this should help.
<requiredExtras>EXTRA_2</requiredExtras>
Edit: Again, I've not forced extras before, that might be totally wrong. There's a chance you need to use <item> tags. I'm not sure, unfortunately. If what I said doesn't work, we'll need to wait for someone more knowledgeable to answer.