We can express this in two words (either/or) already.

The problem is that while there a way to specify the exclusive or, there not a way to specify the inclusive or.

How do you avoid the trap of trying to optimize easy to measure things (like number of words) at the cost of harder to measure things?

I'm not optimizing for number of words. The problem of English isn't that there aren't enough words. It's believed good style to know your thesaurus in English and not say four times beautiful in a row in a single paragraph, even if you mean the same thing. That produces a proliferation of words but not the kind of words I want. When I talk about polysemy I care about the ability to make finer distinctions for commonly used words, where the listener can actually know which distinction the speaker wants to communicate