Honestly, all being said, I would choose the URL structure which makes more sense disregarding the SEO effect. I mean, secure the keyword you want to rank for are there in the url, but do not move them leftward just for the purpose of SEO. As far as I can tell from my little experience is not a factor which weight so much to justify a weird URL structure just for the purpose of putting the most relevant keyword on the far left.
Said that, all the keywords you want to put in the URL must be in the url part processed server side. Crawlers do not process javascript, any framework, like angularjs I mentioned earlier, will make it possible to show different url in the browser through url routing, client side. Which means javascript dynamically change the content of the page without a roundtrip to the server. It's the javascript which detect the URL change, not the server. So the crawler will never navigate it, google will never know it exist.
Yes, there are ways to have google crawler index those javascript generated pages, you can find instructions here https://developers.google.com/webmasters/ajax-crawling/ but I strongly suggest you to do not go that way.
Instead, have your CMS generate an html page with all the content you want to index, and dynamically show and hide portions of the content using a javascript framework like angular, if it helps (for bookmarking purpose or UX) use client side url routing to change the url when you show the different portion of the content. That way google will crawl the page with all the content, it's white hat as long as you don't cloak.
So, what you have to do is design your pages, deciding which content goes there keeping in mind SEO target, keyword diversity and semantic; a part of course from the most important... UX.
Now, getting back to the original question, should you put the keywords you want to rank in the url, yes, put those you want to rank in the url processed server-side, the others if useful for UX, bookmarking, etc... process client side with a javascript framework using client side url routing.
Hope it helps. Good luck.