... just had an aha-moment (is that an English expression as well? ...
Yup. It is, absolutely!
I see now that I'm doing it wrong...
Nope. You aren't doing it wrong, per se. You are doing it in steps. It's like starting your car. You can't do it all at once... you just have to figure out the order of steps. Some can be rearranged, some cannot. So, we have an alias (YAY!). Now, we determine if the alias is valid.
That's not good. Probably also not good for ranking in Google.
Not so! This is where the answer to the 2nd question I asked you is important. If you want the page to not exist, then you are correct. If you want the page "forwarded" to a "error" page, you can certainly offset this.
It sounds like you want the page to not exist. Great!! This is not too bad. Let me ponder for a few minutes while I continue translating your page.
(I've been fixing the way Google is translating your page, just some subtleties, anyhow).
Which option would be best do you think?
In this case, it will be best to just adjust this plugin... So, simply adding a condition inside (after the alias has been retrieved, but before it has been forwarded) will take care of this. Before the adjustment is made, however, do you plan to use site-aliases for any other type of pages (or just locations)?
Wow, 3000, that's a lot!
Not when you consider that it will be a social network/marketing resource for software developers, their development teams, and the projects they are working on/have finished..