Six weeks is enough to rebuild one thing properly. It is not enough to rebuild everything, and a project that pretends otherwise ships nothing.
One tool, one site section, or one design system. Scoped tightly enough that the handover happens inside the engagement rather than after it.
Teams hear accessibility and picture a screen reader. Screen reader users matter, and they are a small share of the people a poorly built page turns away.
Anyone on a phone in bright sunlight needs the contrast. Anyone with a trackpad injury needs the keyboard navigation. Anyone on a slow connection needs the page to work before the JavaScript arrives.
Building for the edges usually improves the middle.
The quickest way to lose a decade of search visibility is to rebuild a site with a tidier URL structure. The new structure is usually better. It is almost never better enough to be worth the loss.
Every inbound link from every article, directory and partner page that ever mentioned you now points at a 404. Redirects help, and they are not free: each one is a hop, and chains of them get truncated.
We keep the URLs and change what is underneath. It is less satisfying and it costs the client nothing.