1) >Lagna, Arudha Lagna, and Bhavat-bhavam lagna and similarly for the other houses to me always represented the TRIMURTI facets of each house. Trimurti, metaphorically, to me represents Creation/Sustenance/Destruction"

2) >"7th (vyaya of ayu bhav from lagna) and 2nd (vyaya of bhavat-bhavam of ayu) are the basis for their being Maraka"

I fail to join these two statements. Do you mean Lagna, 2nd and 8th houses represent  Creation-Sustenance-Destruction ?  Earlier you seemed to imply that Lagna, Arudha Lagna, and Bhavat-bhavam lagna represent  Creation-Sustenance-Destruction. Why you write so enigmatically ?    

-VJ

Array baba, it is straight forward, why do you see twists and turns and googlis in it?

8th is house of longevity (ayu), so by bhavat bhavam, eighth therefrom whis is 3rd will represent the secondary house of ayu. Loss of those is death, hence 2nd (12th from 3rd) and 7th (12th from 8) will represent marakas (death-dealing)
If the 3rd house is stronger than 8th, then it would be destructive to the 8th, in other words would reduce ayu (destructive to attribute of the house in question #8. It is not just ayu aspect, but other attributes too of 8th house. However, on the positive side, the marak potency of the 2nd house would diminish if 3rd is stronger than the 8th and 7th would become more dominant maraka. Note that this is conjectural and not thoroughly researched, yet! Use cautiously but search vigorously!

"this is conjectural and not thoroughly researched" : YES ! Needs practical research.

-VJ

The entire body of knowledge known as Jyotish is conjectural becaue none of the ancient jyotish texts had any illustrations or horoscopes!! Why do you believe in them?

NO, Jyotisha is the Eye of Veda, and the only real science.

-VJ