Yes, good question.
If, linking to an authoritative site on a given topic does lend more "meaning" to your own page, then theoretically, that site will always attract a higher status in G's eyes as everyone will (theoretically) want to link to them too. If the topic is a narrow one you may be knackered - It's the one aspect of this that, if true, irks me.
However, a thematically-written site (or site-section) may be the answer as this adds depth and breadth to the subject-area by defintition. Either that or find a niche by investigatin the related words that the tilde throws up.
Will adding related words without pruning KW's attract an OOP? Not necessarily no.
But what I believe it does allow you to do is to prune the KW's down in the presence of related words - If there is an LSI-type algo at work (and I believe there is as I say), then you don't really need loads of KW repetition - In fact, it could be argued that by overly targetting one KW thru repetition, you're, in turn, overly narrowing the meaning of that page.
It's been posited that G wants to take you to the most relevant site so that the user can hopefuly find the material they're looking for... even if it's not directly on the page served up in the SERPs. An LSI-based algo would/could do that.
Have you tried it? Worked for me though 3-word phrase didn't appear to work.