I think you're very right here. I've spent quite a lot of time trying to sort through the "Why" of Immortalism, but the "How" is the actual interesting + hard part.

The most exposure I've gotten into this space is Seung's "Connectome". I will get smart on some more of the latest (will read through Whole Brain Emulation roadmap) and will email you for sure!

If reality is fundamentally physicalist/materialist, there does not seem to be any fundamental theoretical barrier that prevents us from eventually recreating or simulating every possible personality type combined with every imaginable conscious experience.

This strikes me as a transhumanist version of the Christian 'everyone is reborn on Judgment Day'

I don't know that there is anything much interesting to explore down this path other than, "yes, it does indeed seem possible, but not soon" - but I'm curious if any of the above resonates? At least initially, I'm not especially interested in the resource-allocation constraints.

One idea that slightly interests me is that the typical concept of the Christian Resurrection seems a logical impossibility - assuming personal identity of the "soul" remains intact, it's creating information out of nothing, which breaks thermodynamics laws.

But the materialist/transhumanist version seems only a technical impossibility.

This post from 13 years ago seems to have a tangential take (https://www.lesswrong.com/posts/C5ryrg5ktngwsZHnX/resurrection-through-simulation-questions-of-feasibility)

My Wager
_

I don’t want to die. I like existing and experiencing. There’s a likelihood I (or people in my lifetime) will create technology to make it so that I don’t need to die. But there’s a strong likelihood that this won’t happen.

As time goes on, the likelihood of this technology existing likely increases. And there’s a strong likelihood that the people who create this technology will be in circles that came about from anti-death circles and figures, and will see themselves as standing on the shoulders of these giants specifically. They will likely find these figures specifically and especially important and interesting.

There’s a strong likelihood that, if possible, they’ll try to bring these figures back to life. Entropy will have reduced the available primary source information about these people down to close to zero, but depending on the circumstances, maybe not precisely zero.

My primary objective in life is singular: solve for my own death. But failing that, I have two secondary objectives:

1. Become important and interesting to the future people who will solve death
2. Provide these future people enough primary source information about myself so that entropy hasn’t reduced me down to zero