You have covered the most important items.
1. If possible, keep the same URL structure. If that is not possible, be certain all the URLs are properly redirected (301) to the equivalent pages on the new site.
2. Ensure the new site's navigation is solid. Perform a crawl of the old and new site, or generate a sitemap for both sites. Compare the URLs and investigate any discrepancies.
3. You should investigate all the normal SEO factors to ensure they are in tact between sites. Header tags, meta descriptions, meta tags such as index and follow, robots.txt, alt tags, etc. should all be inspected.
4. You should check to ensure the new site uses valid HTML/CSS. While not directly SEO related, invalid code often causes issues where your site does not appear properly in various browser versions. Your pages can easily be checked with the W3C validation tool.
5. Minimize flash on the new site or, if you do use flash, ensure you have the proper HTML support. You can disable flash on your browser then view your site to verify.
6. You should check your site security after moving to the new CMS.
7. Ensure your daily backups are created on an automated process. TEST IT! Perform a site restore to a test site after your first day of being live.
8. Ensure you have a "friendly" 404 page. Offer a search box and your normal site's navigation so users are more likely to stay on your site.
9. Check your site's page load speed with PageSpeed or YSlow.
10. Make sure your client has a solid process in place to handle maintenance. A current client had an issue where after his software was originally installed he never updated. His site was hit by malware as a direct result. A plan should be established as to how software updates will occur.