My friend  prismakari wrote a short piece regarding this particular facet of macro, and did a far better job expressing my love of absurdly-huge macros than I would have been able to write. So! With their blessing, I share with you what they shared with me:

"I was just thinking about ultra/omni macro stuff, and the mechanics of how it works at that scale.
Like... we produce speech by expelling air from our lungs, but at a planetary scale, any air we breathe out would travel so slowly - not to mention the speed of sound being such a limiting factor - that it would just be impossible.
At an order magnitude bigger, even a simple sweep of the arms would travel faster than light, and the mind bends as to how that would look to both the colossal entity or to any observer, let alone the ramifications for relativity.
And I know what you're thinking. This is the point in the conversation where I say "Hey, wait! Where are you going? Come back!"
But I'm going somewhere with this. I'm not just here to nerd out and "Um, ackshually...” over the scientific impossibilities of macro smut.

That was just the preamble.

Because it got me thinking.

I find myself attracted to the idea that, at those sizes, one ceases to interact with - or even be CAPABLE of interacting with - the universe on anything resembling a recognizable scale.
Your very existence breaks reality, and you become less a large entity and more a... fundamental physical fact of the universe.
When you're so large that the simple rise and fall of your chest while breathing exceeds the speed of light by several orders of magnitude, you cease to be bound by those things our physical reality defines itself by.
Your perception is unbounded by light's medium, and so there is nothing you cannot see or know or feel.
Reaching across Time itself, forward or backward, becomes as simple as putting forward an outstretched hand.
Your very being would be impossible to conceive by those bound to a terrestrial existence.
You transcend mortal perception, and to them your existence might only be a warm, curious feeling in their chest when they gaze into the night sky.
And to you, the mortal world has ceased to be within your abilty to touch on a scale so infinitesimal and crude as a planet on a recognizable time-scale.
What might seem to you as coy bat of the eyelashes, a gentle and flirtatious bounce of the breasts, or an orgasmic climax would, for the Universe, play out in the peculiar motions of the Stars across millions of years, propagating forward and backwards through time across tremendous spans of Existence, presenting as a theoretical-model-breaking head-scratcher for astronomers the galaxy over.
Your every breath and motion ripples through the cosmos, through both the future and the past, and you can reach so far back that it becomes a simple fact that You and the Universe both Exist because You Always Have and Always Will.

And, uh...

Not gonna lie.

I find that kind of mega->giga->ultra->omni macro growth, ascendance, and transcendence to be kind of incredibly hot."