Purely guessing, but, as far as I'm aware we don't know know what happens to an exo's consciousness when they die. Perhaps they're reuploaded to the original body? So, sure he wouldn't be a guardian, but he'd be alive, somewhere on enceladus in the deep stone crypt.
If anyone can find evidence for this, or completely disprove it, please let me know.
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Original body? Why would they hold on to that? Even if they did you'd think that the collapse mixed with a couple thousand years would have completely destroyed whatever cryo pod it was stored in