Where to begin? Well let's start with the obvious. "So why haven't you killed me already too?" / "Well I had to gloat about all this to someone". Remember what I said last time about the Empire not being competent? I'm sure the Evil Overlord List says something about gloating, and the standard trope is that when the villain gloats instead of kills, the rescue is about to happen. And our heroes a.k.a. the daughter who wants to kill them is on her way. But now I think about it, so is an airstrike.

Now, an ocean planet. Earth is an ocean planet. This was addressed nicely at the start of Lilo and Stitch, where the alien council was watching the rocket ship with Stitch landing on a planet that was 70% water, aiming at a hemisphere that was entirely water, and hitting a tiny little island in the middle of nowhere.

So let's say you've got a planet with a hot lava interior. That hot lava interior is going to be sending volcanoes up. That is going to form islands. Your ocean world isn't going to be solid ocean. If it is solid ocean, with no land, then it doesn't have a hot interior, and without a hot interior, it won't have the liquid iron that makes a magnetosphere, and my understanding is that without that it won't have protection from the solar rays, and then you expect the water (and the atmosphere) to be destroyed/blasted away by the oncoming radiation.

The only other alternative is that this is some sort of strange water world that has a solid water core that you could just dive through. And as much as I'd like to say that's strictly something out of science fiction, I'm reminded of just how weird some of the alien planets we have already found have turned out to be. But I'd still like to know how it generates a magnetosphere, or stays hot.

Seriously though: you're not going to look for sand on an ocean planet? An ocean planet with no beaches anywhere? And your plan is to bring in several hundred star destroyers' worth of sand to make an artificial island? And that artificial island is somehow not going to be destroyed by the ocean waves? (For that matter, what do the man-made artificial islands use to keep together? Alexander solved that a long time ago in an empire far away ...)

The one thing in this plan which isn't a problem is the traffic of the ships. If you're bringing in a star destroyer a minute full of wood - 1440 per day - a couple of hundred making a trip from Tatooine is almost noise. Except of course, there's some Black Alpha people on Tatooine who would probably notice. The Empire doesn't know about that though.

But you just know, absolutely predictable, that if a data archive is "ultra-secure", if you are absolutely sure that no one will ever get their hands on the plans, then you can be certain that you will never be able to get the data yourself when you need to. So presumably, the Rebels will get a copy of the data, and the Empire will not be able to get another copy of the data.

Remember people, test your off-site backups. If you cannot restore your data, then you know your backup system is not functional. (Of course, if you attempt to restore your data and it fails, do you have your originals anymore? The advice to test your backup system has always struck me as questionable, because you will need another backup system if the one you're testing messes up.)

— Keybounce