predators was my problem too.
When we built the new coop, we actually lined the walls w wire before the wood outside. It helped keep a lot out for awhile, but eventually rats chew thru anything.
Not sure a substantial layer of wire will prevent digging if there's a 'seam' at the floor to wall space?
If you do the wire outer floor, perhaps consider starting it near the base and bending the wire to have a continual 'wall'?
Also, consider that a low to the ground electric fence will keep a lot of critters out, and is easy to keep brush free and is a lot less perimiter than a 4 ft wire floor to care for over time?
A wire roof keeps out the hawks and anything that climbs the walls. (electic fence helps keep the ground ones from attaining a wall, but won't help against fishers or martins. Fishers especially, will come from the tree's as much as from the ground. And, once you've every heard a Fisher rally cry, you'll never forget it. ugh....)
It feels like a prison but it'll keep them safe. Mostly, keep them safe at night!!!
One thing I did, and I think it was something I did right, was to offer the grass clippings to the birds when I cut the grass. They loved it and it became thier 'fresh greens' once we had the big yard penned in. They all perked up whenever we started the lawn mower
Good luck and have fun!
My outlook of 'live or die' especially when hatching, was :
don't coddle the weak ones. You can try, but consider that the strong ones survive for a reason. If you manage to raise what started out as a weak chick, it may not be the strongest chicken and you can dimish your birds by keeping them all.
It is sad to lose some, and especially when they are so small and fragile, but find good care practices, stick to them, and the strong ones will be your rewards.
Cheers
Jenny