[BroJoeK]

jeffersondem quoting: "In their own words: '. . . to institute new government, laying its foundation on such principles and organizing its powers in such form, as to them shall seem most likely to effect their Safety and Happiness.' "

But as always, you misquote by taking those words out of context.
The full context includes these words, among others similar:

"That whenever any Form of Government becomes destructive of these ends, it is the Right of the People to alter or to abolish it, and to institute new Government..."

So neither here nor elsewhere in the Declaration is there any hint of the term "at pleasure".
Instead, it's all from stark, brutal necessity.

No such necessity existed in 1860 when Fire Eaters began to declare secession at pleasure.

Of course, at pleasure did play a big role in the 1787 Constitution -- with "secession" from the Articles and ratification of the Constitution by mutual consent.
But there was no such mutual consent in 1860.

[jeffersondem]

“So neither here nor elsewhere in the Declaration is there any hint of the term “at pleasure”.”

The words “at pleasure” do not appear in the DOI in any context; the words were inserted into hard-shell, northern Mother Church dogma much, much later.