One premise of this hypothetical analysis has now come true. https://www.lawfareblog.com/presidential-succession-nightmare

If you want to get up to speed quickly on the constitutional debate, I would start with this article by the Amar brothers. https://digitalcommons.law.yale.edu/cgi/viewcontent.cgi?article=1959&context=fss_papers

I would then read the response by John Manning. https://papers.ssrn.com/sol3/papers.cfm?abstract_id=2854357

Here is the report on this by a bipartisan commission a decade ago, under the veil of ignorance, so to speak. https://www.brookings.edu/wp-content/uploads/2016/06/06_continuity_of_government.pdf

And here is the best contemporary take on the view that the succession statute is constitutional, by @JoshMBlackman and @SethBTillman. https://www.theatlantic.com/ideas/archive/2019/11/2020-election-could-pit-pelosi-against-trump/602308/

This book by Brian Kalt has a good chapter on the problem. https://yalebooks.yale.edu/book/9780300123517/constitutional-cliffhangers

Other relevant analysis:

https://scholarship.law.edu/cgi/viewcontent.cgi?article=1237&context=lawreview

https://harvardnsj.org/wp-content/uploads/sites/13/2020/04/Tillman_Why-Strict-Cabinet-Succession-Is-Always-Bad-Policy.pdf

https://www.everycrsreport.com/files/20081003_RL34692_23adce9970abd6658fdfb322316c2ac32f3660b5.pdf

https://law.hofstra.edu/pdf/academics/journals/lawreview/lrv_issues_v39n03_cc-1-albert-final.pdf

https://www.jstor.org/stable/1229153?seq=1

Also worth including: Acting attorney general McGregor's 1947 letter to the chairman of the House Judiciary Committee, concluding that 1947 Succession Statute is constitutional because members of Congress are “Officers” under the Succession Clause. https://assets.documentcloud.org/documents/6818250/GPO-CRECB-1947.pdf