Are any of the t-glottolization, th-fronting, h-dropping, etc. in English a phonological complex?

Question

Wikipedia gives the following, with plenty others ommitted by me, as some of the features of Cockney English:

T-glottalisation: Use of the glottal stop as an allophone of /t/ in various positions,including after a stressed syllable. Glottal stops also occur, albeit less frequently for /k/ and /p/, and occasionally for mid-word consonants. For example, Richard Whiteing spelt "Hyde Park" as Hy' Par.

Th-fronting: /θ/ can become [f] in any environment. [mɛfs] "maths". /ð/ can become [v] in any environment except word-initially when it can be [ð, ð̞, d, l, ʔ, ∅]. [bɒvə] "bother," [dæɪ] "they."

H-dropping: Sivertsen considers that [h] is to some extent a stylistic marker of emphasis in Cockney.

Rhoticity: A rhotic (pronounced /ˈroʊtɨk/, sometimes /ˈrɒtɨk/) speaker pronounces a rhotic consonant in words like hard; a non-rhotic speaker does not. That is, rhotic speakers pronounce /r/ in all positions, while non-rhotic speakers pronounce /r/ only if it is followed by a vowel sound in the same phrase or prosodic unit.

My question is, are all these myriad features independent? Or do they form something of a phonological complex, where a dialect gaining one feature would predispose it to gaining all or some of the others?

(I ask because I wondered if there might not be a simpler characterization of these accents in terms of only what the lips, teeth, and tongue are doing. For example, I feel like Cockney speakers tend to spend a lot of time with the tongue near the back of the throat; could that be a passable explanation for all the features of their speech? My simple method of generating my approximation of Received Pronunciation is just keeping my teeth more "stiff" as compared to my American accent. I was wondering whether such simple "rules" as above -- not likely to be correct, but the point still stands -- could generate all the differences between American and British dialects, which would require a phonological complex. I think.)

Answer 1

OK going off the top of my head:

• "Standard" British English has just non-rhoticity out of the four you mention.
• Cockney (naturally) has all four.
• The dialects around where I grew up (in the south of England), have all the features except (usually) Th-fronting.
• Scottish dialects are generally rhotic, often have T-glottalisation, but usually not the others.

Clearly this is far from sufficient evidence to draw any firm conclusion, but it does begin to suggest to me that the features are probably independent...

Answer 2

They certainly account for some of the differences between various dialects. I'd have thought that the major phological differences were in the vowels, though. I'll see if I can come up with any links to research.

Edit: I see I've misunderstood the question somewhat. Believe what @psmears says!