You seriously want me to untangle all of that?
The fundamental flaw of your position is to treat other people's wants as fungible if there is something that can achieve something similar. They are not.
I wanted onfoot gameplay, did I get everything I wanted from it via Odyssey? No, but that's because I can think of a zillion things that can come with it. Did I want what Frontier provide? For the most part yes, and I look forward to it being expanded to include some other linked gameplay that can use onfoot mechanics that require an overhaul of other aspects of the game to accommodate. Stuff like ship interiors, real cities on ELWs... and base-building.
Big enough that some would prefer x vs y given the choice?
Look, it's clear that your position on the matter of base-building is in opposition to it. That's fine, but I'm not sure what you seek to achieve by telling people that somehow they don't want base-building when they clearly do and can elucidate on why they do.
I know the general talk here is "what is the new feature going to be", which opens up a certain degree of potentials, depending on whether Frontier are talking about an update for Odyssey or a brand new paid for expansion - of which either are welcome to me, and maybe I actually might prefer it being a paid expansion actually, but I digress..
The bottom line is that it's the same as I've said before; Frontier can't develop all the features at once and some are hierarchical from a technical or developmental standpoint, which means that sometimes x has to come before y. I'm not saying base-building is one such feature, but then I'm not privy to the order of development, maybe there are aspects of base-building that can be built upon to implement ship interiors down the line. Who knows? The overall feeling that it will be base-building obviously comes from the leak that said that it was coming, whether that pans out or not, we will see.
What is clear now, and has always been, is that there is always going to be some group, large or small, who want y vs x. This is unavoidable due to the above fact that Frontier do not have unlimited resources to develop everything at once and the scope of the game means that there are a lot of great ideas that would work well in Elite. What is avoidable though is the outcry from x segment of players who didn't get y feature implemented. And if it was converse; y segment of players shouting about why x feature wasn't implemented. My question is what the point of all of that is, and to whom's benefit is it? Surely not anyone who wants to see Elite Dangerous progress or claims to be a supporter.
As an example; If you asked me if Power Play was the number one feature I wanted overhauled I would say no, but it is completely fine with me that it is as it is number one for another group of players and I'm glad the game is moving forward for them, and I'll be sure it check it out too. What I'm not going to do is tell Power Play players that some how an overhaul of Power Play isn't what they really want.
I think base-building could be really cool, I can see in many ways how it would benefit the game, I can also see potential problems and share some concerns in relation to implementation. But none of us know if it is going to be base-building, and if it's salvaging via ships, or whatever it is you'd rather it be, I'm sure I will be just fine with that too, with same caveats and concerns about implementation etc.
If it turns out to be base-building, I'd say give it a chance, even if it's bottom on your preference list.