This also utilizes the o-layout--row-reverse--l class. Maybe a good thing as far as SEO goes because the content would come before the menu.

<section class="o-layout o-layout--row-reverse--l">

<div class="o-layout__item u-width-12 u-width-10--l">
	<div class="o-layout">
		<div class="o-layout__item u-width-12 u-width-9--l">
			CENTER 9 col on desktop, TOP ROW on mobile
		</div>
		<div class="o-layout__item u-width-12 u-width-3--l">
			RIGHT 3 col on desktop, SECOND ROW on mobile
		</div>
	</div>
</div>
<div class="o-layout__item u-width-12 u-width-2--l">
	LEFT column on desktop, LAST ROW on mobile
</div>

</section>