zAchAry
It is the same issue in both screen shots.
That message is related to a timeout feature in the javascript engine for stopping endless scripts due to performance reasons.
The value in my profile was 10 sec. For instance, increase it to 15 in [url]about:config[/url].
dom.max_script_run_time ...

The meta packages are the easiest thing. Just create some dep files, use depcheck and there you go.

Installing an extension for all users
To install extensions for all users it is necessary to have write access to the office installation. Open the Extension Manager dialog via Tools-Extension Manager and click the "Add" button. After having selected an extension one will be asked to install it for ...

Finally, not everyone requires Xorg, what if your setting up a server for example?
That's exactly the main point that puzzles me.
EDIT
If the user downloads only a core installation in the first place and decides afterwards to install as well X, so the wizard has to download all needed X packages ...

Download the SLKBUILD manually in a new folder and run there Finally, you should be able to install the built package.

Very cool

Sorry, but the idea behind is top secret for understandable reasons. Maybe a little surprise for X-Mas ;)
I think the Xorg packages should be kept in the iso file due to most people would like to have at least Xorg running, independently what intention for the target system is planned.
This is the ...

Why purchase an URL? No, just kidding.

That book is available to buy as a printed edition, isn't it?
Who will get the money and which companies will I support with the purchase?

Please let me kindly ask: Which book exactly?