[Porsche-O-Phile]

I'd also be concerned about eccentric loading and seismic loading. Since you can't pound joist hangers into the pool perimeter (well, maybe you can but you'll destroy the pool) you're going to have to cantelever the ends of the floor joists off the supporting beams for some distance. This is fine in most cases, but one does need to consider the loadings.

If you're using 2x8s or 2x10s, it'll probably be plenty strong for the deck loading itself, but you also need to consider how the loads are transmitted to the soil below (it looks like you've just got a couple of columns bearing on the pool bottom, which may very well eventually fail/crack due to point loading in that location). If you're not going to use the pool as a pool ever again, it might be worth coring out the bottom under the columns and sinking in piles or pouring standard footings. Much stronger than bearing on what effectively is a slab-on-grade.

If an earthquake hits, make sure to lift up the deck and check the walls of the pool underneath for cracks. Essentially you just have a continuous retaining wall there that's resisting who-knows-how-much lateral force/hydrostatic pressure. When the ground starts moving, since the volume inside is empty (rather than full of water) it might be more susceptible to cracking/failing.

Just some thoughts to consider, which you may have already. . . I like the idea actually, but if the end goal is family safety, it needs to stay true to that goal in its execution - every detail.