Make sure your team lead/dev team hires a UX consultant/contractor. There is too much money on the line to "think" you know what your customers want from a design standpoint. This affects SEO and beyond.
Implement meta noindex, nofollow tag on all pages to avoid crawling of pages
Add Disallow: / to robots.txt file to block robots from crawling site
Make sure rel next prev canonical tag is implemented on paginated pages (side note: yes Google deprecated this recently, but it is still recommended for other search engines)
Review all schema types and test with Google\'s rich snippet testing tool
Review meta tags (via site crawl and testing with user agent Googlebot): title tags, h1 tags, meta descriptions; make sure you port over from old site to new site - DO NOT PERFORM KEYWORD RESEARCH AND CREATE NEW TAGS UNLESS IT\'S A NEW PAGE.
Review alt text implementation: run site crawl
Get a list of any "junk" urls and query parameters to add to Google Search Console and robots.txt file
Run a test order of Google Analytics, Tag Manager, Adobe, or whatever analytics platform you use to make sure data is being passed properly
Make note of internal site search settings you need to adjust in analytics before launch