Yes, that approach I put there is more philosophical, and the problem you comment arose immediately, even having in mind the coordinate system implied in the original post, in Bad Conlanging Ideas. That's why I suggested further expanding the lexicon with compound words; it's clear that the system is exhausted quite soon applying the basic idea.
    My problem with the IPA vowel chart is not so much that the number of sounds is what it is but that I don't/won't have a language using all of them. In any case, I don't to work with a vowel fuckfest!

In a certain way, what I said in the other post is what I've been doing in Mintani to derive some words: affixes are used, but also word/root modification playing with vowels. Not the exact idea but pretty close. Anyway, a nice idea that I'll explore more in depth.