@sasha said
"If you see the LRP in these ways, then how do reconcile the two? Which sephira serves as earth?"
It's really not an either/or choice. The two ideas coexist. There are multiple paradoxes from this since, for example, Mikhael that is Archangel of Fire is not the same as Mikhael that is Archangel of Mercury and Hod, even though the two schemas both put Mikhael in the same place.
"It seems so much easier and more elegant to me to see it as all taking place within Malkuth."
I don't think that's a conflict, either. Remember, this ritual was a Golden Dawn invention. In the Golden Dawn, the entirety of the First Order (below Portal) consisted of sub-Sephirah in Malkuth. Therefore, saying that it is laid out on the tree just below Parokheth, and saying that it is "all in Malkuth" are - in the scheme for which it was created - pretty much the same thing. (One gets into trouble when one starts trying to interpret this ritual outside of the context for which it was custom-created.)
"You don't have to swap archangel positions or make any substitutions between Uriel and Haniel. You can also keep the elemental focus if you want, but a focus on the elements within Malkuth, rather than the "greater" elements associated with the four lower sephiroth."
Well, you have the problem that three of the four archangels are in the wrong place if you do it as the Elements as arranged within Malkuth.
Foolhardiness is not courage.