I guess that is why it is important what you decide the biblical context of Gen 1 is. I think the biblical context is establishing God’s reign. So, I think the focus of creation week is the domains encompassed and ordered by God’s rule, not the method or chronology of material creation. (More thoughts on “speaking” and creation to follow.) Even setting aside the Walton functional/material distinction, the idea of the creation week setting up domains of God’s rule which are then filled with inhabitants is found in the framework interpretation that sees Genesis as a historical (although poetically figurative) account of material creation.
As I understand the Sabbath, it was a sign of the covenant. (“the Sabbath is a sign of the covenant between me and you from generation to generation. It is given so you may know that I am the Lord, who makes you holy.”) The covenant was given so that God could establish the glory of his name among all the peoples of the earth. So the observance of the Sabbath seems to me to be primarily about glorifying God among the nations.
The Sabbath, although it benefits people to rest from labor, is primarily an act of worship that is supposed to point the watching world to the Lord of heaven and earth. People order their own lives and provide for their own well-being through work for six days, but on the seventh, they acknowledge that there is only one king on the throne of the world, and that king is the Creator God who has been ruling since he took up his rest on the throne of his temple on the seventh day of creation. All ordering of chaos starts with him, all provision for creation depends on him. All our work is done in our role of stewards and representatives, not as autonomous rulers who can make a name for ourselves through our labors (like they tried to do at Babel). It seems pretty clear to me that the institution of the Sabbath and the honoring of it by his covenant people is more about living humbly under God’s rule and reign than it is about imitating God by taking a break every seven days.
I think this idea of recognizing God’s lordship in the Sabbath fits well with the idea of Jubilee too. Jubilee was also a Sabbath designed to point to God’s ultimate lordship over his people. No one could build up a kingdom for themselves if every 50th year property was redistributed and God’s ordering of the land and society was reinstated with the freeing of slaves and cancelling of debts. A year of living off of God’s provision, not human effort sounds a lot more to me like an exercise in obedience and submission than just a vacation for people. It was a chance for Israel to do something no surrounding nation would imagine doing in order to give God glory for his provision of their needs and sovereignty over their people. (Lev 25:10-12)