LanguageLocalizedURL module isn't in active development anymore because we now have this functionality in core with LanguageSupportNames which is the way to go now. LanguageLocalizedURL was created because the lack of names per languages and created by mcmorry and me.
What I meant is using a page field that uses checkboxes as input to make languages active or not for a page. The input for the page field comes directly from the language pages found in admin (each language is a page). This enables you to turn off also the default language and at a small price. This page field then can be used to not find or show pages which aren't active even the default language. It's just a matter of a few lines of code to show the 404 when a page is accessed that isn't active.
I get what you're saying but thelanguage system doesn't work like this and you always have to enter default title and name when creating a page. The way it is built I think it made the most sense for most use cases and it wasn't in from the start. It's a module that came to it and the default language is required because you can install and uninstall it. So there's so many things to consider and pros and cons, no language system is perfect and may not suits your requirements. But PW is enough flexible and customizable to work around it and give waht you need even when you have to enter the default lanugage title and name I think it's a small issue considering that PW gives you in term of multilanguage features. I and my client can live with it as it's not something of a problem that big.
I don't now what Ryan thinks and if it makes sense or is even easy possible to implement a "not have default" language require. Maybe it is easy and I'm not seeing it or there's a better workaround, but so far I have to use whats there and try to use it as best as possible.
If the project requirements fit, still the most flexible and best way to create multilanguage sites that can differ in structure and not are based on a default language should be built using separate branches for each language and connect them using page references. There was a module in development (Oliver) that would help managing sites like this but I don't know what happend to it as it doesn't seem to be active anymore since a long time. Building it this way enables you to have each language as it's own page and can be much more flexible and practical the way you can build your site and be free from restrictions coming from a language system that assumes things you might don't want.