My belief is that you don't have do anything, because it doesn't matter anymore. Might as well stay technically alive.
"For a few thousand years now we are in the process of out-growing our original substrate"
We're still not there. If we had uterine replicators, the problem we're discussing would be a non-issue.
But, we don't. So it's a huge issue. We have to stay alive, and we're all dead in less than 100 years. Therefore, we have to reproduce. Surely we also have other goals, but reproduction is a sanity check on those.
Maybe we can tear this chain apart one day, but we didn't yet.