I don't want to fight you (though honestly, this looks like an attempt to organize a fight between your fans and people who disagree).
But there are very simple arguments that make these ideas impracticable (micromanagement, little benefit for a lot of work, bugs and balance problems).
And it's completely useless to try to justify that with argument about how realistic it would be (of course people love to discuss that on the forum, and there will always be someone to contradict - but really, that Vietnam argument is silly, and we all know that bombardment in Stellaris doesn't work like that, and also that guerilla fighting would be very boring very fast), and funny to try to make "grand strategy" mean what you want it to mean. The thing about space opera not being about space is also quite entertaining (especially since you know Star Trek...). Stellaris is not the Dune kind of space opera and that won't change.
Just rework your idea so it is better. Don't spam the entire community on all media with it, please... For example, leave behind the continents, it's simply not efficient, and I'm sure that you are aware it's just something you'd really like to see personally, but that doesn't enhance anything for the combat system.
I would agree with that. My disagreement is with the whole surface/ground troops are completely irrelevant position that seems to always appear from any "no, making ground combat more involved is a bad idea" from a "the attackers can always drop asteroids on the planet" position.
So I think there should be the scope for something a bit more interesting than the current mechanics for planetary conquest (which, tbh, I would agree could be taken out entirely without losing much from the game) because there is more to actually controlling a world than just naval superiority under circumstances where the attacker does not want a heavily damaged world to start again with on colonisation.
Not all life is made equal. Even if it can breathe our air, it can't eat our food.
Destroying biospheres would be a necessary element of pre-colonization.
The current mechanics of the game imply that is not the universal case, otherwise, multi-species planets would not be a thing. There are scenarios under which having a not totally devastated planet would be desirable.
......
My personal feeling is that a system which has dynamic interactions by the player, but doesn't require much in the way of micro involvement, and which recognises the need for capturing and controlling the planetary surface in certain circumstances, and recognises that establishing that sort of control can be (made by the defender) very difficult, is the ideal version of how it should be.
I did at one point kind of like the idea of wars playing out on surface tiles, but I would agree that that would be far too micro intensive on anything but the smallest of maps.
Something which is event driven, and in which you can influence the events through policy/edict/building/etc choices made before, would be, I think, ideal.