Are we talking about non-rationalists, or non-x-rationalists? With Traditional rationalists (free thinkers, skeptics and the like), it seems that you could indeed phrase both of those issues are purely engineering problems with the strategy you are proposing, and expect some payoff.

With non-rationalists, however, it seems like the biggest part of the problems are these:

With strong AI, it is overcoming the tendency that people have to associate it with some foggy ideas about 'consciousness' they have cached, and thus conclude that it is 'beyond' the category of 'mere engineering problem'.

With cryonics, a somewhat related issue occurs with the association of death with a 'soul' or an 'afterlife' and cryonics. When you get into the specifics of reviving the brain, similar issues about 'consciousness' can arise as well.

That said, I might bring up the notion of printable organs.