One thing I like to do is to not only use the readings I assign for class as discussion points but also as writing samples. I'll pick out something the writer does well, be it structure or a particularly good paragraph or use of quotes or whatever and try to guide my students towards understanding what the author is doing so they can try to emulate it or do something wildly different. But at least it's a break from the dreaded five paragraph essay. So if you want to see if you can break out from what you've always done, start by looking at what other people are doing and go from there.
Yes, this is great - and if you do this with a number of different writers who are excellent writers but very different in style (contrast, say, Annie Dillard, with Martin Luther King Jr.), students get the sense of how you can arrive at ideas by way of different, but all effective, routes.
The more complicated the thought, the longer the words, the longer the sentence, the longer the paragraph.
Not necessarily. A very complex thought can be communicated with relatively short words (they just have to be well-chosen!
) and with short paragraphs and sentences (though, ideally, I'd say, you always have a mix of kinds of sentences and paragraphs - some longer and more complex, some simpler and punchier).