In Part II of The Coherence of Theism (revised edition), Richard Swinburne discusses the idea of a “contingent God”. This is because the characteristic of “necessary being” makes it so that, according to Swinburne, the concept of “God” cannot be defined in ordinary and non-stretched words. So, in Part II, Swinburne sets aside the property of being a “necessary being” to show that the other characteristics implied by the word “God” can be clarified and understood in terms of ordinary words understood in a straightforward and non-metaphorical way.

In order to try to show that the sentence “God exists” expresses a coherent claim, Swinburne analyzes the concept of “God”, and then starts with one piece of the concept and slowly builds back up to the full concept, adding back one piece at a time, and arguing at each step of the way that “X exists” expresses a coherent claim, where the “X” includes one or more pieces of the concept of “God”, as understood by Swinburne (technically, “God” is a proper name, so Swinburne is actually showing that the sentence “A divine being exists” expresses a coherent statement, where “divine being” is a category that includes persons who have a certain set of characteristics).
Here are the pieces:

• an omnipresent spirit (Chapter 7)
• who is perfectly free and is the creator of the universe (Chapter 8)
• who is omnipotent (Chapter 9)
• who is omniscient (Chapter 10)
• who is perfectly good and is a source of moral obligation (Chapter 11)
• who is eternal (Chapter 12)

Swinburne’s first step is to show that the sentence “An omnipresent spirit exists” expresses a coherent claim. The second step is to show that the sentence “An omnipresent spirit who is perfectly free and who is the creator of the universe exists” expresses a coherent claim.
The description keeps expanding until Chapter 12, where Swinburne tries to show that the sentence “An omnipresent spirit who is perfectly free and is the creator of the universe, and who is omnipotent and omniscient, and who is perfectly good and a source of moral obligation, and who is eternal exists” expresses a coherent claim.
I’m not clear why Swinburne chose to begin with the characteristics “an omnipresent spirit” , because it would make more sense to start with the characteristics that he believes constitute the logical core of the concept of “God”, namely omnipotence, omniscience, and perfect freedom.
Swinburne argues that the remaining characteristics are logically implied by these key characteristics:
…a person who is eternally perfectly free, omnipotent, and omniscient will have the other divine properties which I have considered. He will be an omnipresent spirit, creator of the universe, perfectly good, and a source of moral obligation. (COT, p.232)
So why not start out with the sentence “An omnipotent person exists” or “An omniscient person exists” or “A perfectly free person exists”? According to Swinburne, the characteristics called out in these sentences logically imply the other characteristics (omnipresent, spirit, perfectly good, creator of the universe), so it seems more efficient to first show the core concept of “God” to be coherent, and then show that that core concept implies the other characteristics.
I would have first tried to show that this sentence expresses a coherent claim:
(1) A person who is eternally omnipotent, omniscient, and perfectly free exists.
If I accomplished that task, then I would use that conclusion to show that the following sentence also expresses a coherent claim:
(2) A person who is eternally omnipotent, omniscient, perfectly free, an omnipresent spirit, the creator of the universe, perfectly good and a source of moral obligation exists.
Instead, Swinburne begins with a sentence that includes some characteristics that are not part of the logical core of the concept of “God”:
(3) An omnipresent spirit exists.