Welcome to the Q&A Forum

Hi CJ, I can't imagine a situation where I'd want to do this, but I'm sure you've done the analysis to determine that it's better for your UX. Just make sure you consider this: Not sure what you're using to make the nav dynamic, but you should make sure Google sees it the way you intend. You can use the Fetch and Render in Search Console. You can also use the first part of this inforgraphic to set up a browser to view your site in a live environment the way search engines see your site. You'll want to make sure that once you've disabled CSS and JS that your navigation is still visible. A lot of authority/juice/whateveryouwantocallit is passed through your nav. Having your nav visible this way also ensures quicker crawling/indexing of new content on your site.

Applying Broken Windows Theory to SEO is such an underrated tactic. It's totally worth the time. Will you be able to directly attribute revenue to the cleanup? Probably not. Will it improve the overall quality and user experience of the site? Absolutely, 100%, and that's where it becomes an SEO play - because that better quality and better UX exactly what Google is aiming to reward in the long run. And because your site no longer looks like an easy mark for spammers, it should attract less spam in the long run. Also, adding to MattAntonino's comment, Paul Haahr said a few weeks ago that the quality rater guidelines are basically Google's ideal algorithm, so you can count on Google working to incorporate as much of that as they can into the algorthm over time as they figure out how to automate it instead of relying on human maintenance. So even if it's not there now, count on it being there in the future. Future-proofing is always a good idea.