One issue that hasn't been raised is the time limitation for safely staying in cryo. Merlin figured it at 40 years or so, and that was pushing it. That's why one of the theories of what's under the temple (or on the
Hamilcar if it still exists and is in an elongated orbit) is that shifts of "archangels" and crew are alternately waking from cryo, exercising, taking their life extending drugs and updating their nannites, then going back into cryo again - for no more than 40 years at a time, and probably much less than that.
Operation Ark required 8 million colonists to remain in cryo for 18 years. That was a HUGE risk. I imagine there were undoubtedly thousands, if not tens of thousands of casualties. Staying in hyperspace much longer simply wasn't an option, since the death curve for those in cryo would climb steeply as the years passed. Keep those millions in cryo for 40 years or more, and who knows what percentage would have survived? It wasn't a chance Merlin would have liked to take!
Admiral Pei figured 500 years were enough to prove that they'd escaped not only the Gbaba sphere of influence, but also any scouts the Gbaba may have sent out searching for any secret human colonies, but he added a 50% margin and woke Merlin up after 750 standard years. (We also have to remember that RFC's editor "fixed" the calendar in OAR and overlooked the fact that the calendar used on Safehold begins at the end of the War of the Fallen.) Suffice it to say, well over eight Terran centuries have passed since Operation Ark got underway.
The original plan anticipated 300 years or so for any Gbaban search to end, after which high tech would be reintroduced, giving Safehold time to develop superior weapons and ships that could destroy the Gbaba by the time the Gbaba detected Safehold's emissions. (And no, we don't know how far Safehold is from the nearest Gbaba outpost.) Obviously that period has been vastly extended, which doesn't mean any signals that Safehold generates (especially neutrinos) won't reach the Gbaba just as quickly. However, the Gbaba have likely stood down from the high alert status they were on while battling and destroying the Terran Federation. That ought to give Safehold a bit more time - and the ability to destroy any Gbaba scouts that arrive to check out the emissions created during the buildup period.
Another benefit of the delay is that the population of Safehold is much greater than it was several centuries ago. So if everyone could just be convinced by the Great Reveal and get on board with kicking some Gbaba posterior, the process should progress faster than expected, especially if the
Hamilcar still exists, which was part of the original plan.
The first attack of the Safehold Federation on the Gbaba will come as a surprise... The last one will be inevitable.