Coming in a bit late to the party, enjoyed reading through the back-and-forth.
Another consideration for "in at the start" is the structural aspect of the site. Things like domain name, folder names, and page names all play a part in the searchable-ness (?) of your content, and by extension your choice of website development tools/frameworks. (Ever use an open source forum that insists on naming posts with cryptic page names? Good luck trying to get that to be more searchable.)
I agree, though, that getting in on the ground floor is not always an option. That's why it's important for us
SEO types to rise through the ranks and seize control of our company so we can be sure that we're there!!