I don’t blame you. Plywood ain’t gonna last long. Good for a quick make it work situation, but I’m glad you’ve got a plan to make it more like a deck with solid wood decking. I will give you a word of caution though, pallet strips are normally about 3/4” thick in my experience, which may end up leaving you with some sag. Codes in the US generally spec 5/4 decking (1” actual) with a 16” on center span between joists (works out to about 14 1/2” open space inside of joist to inside of joist), and that’s on 2x6 joists. I am not generally one who follows codes because “it’s the code”, but in this case doing less than the code usually winds up with some saggy/spongy feeling deck.

I say all that to say that when you go to put those boards down, place enough to stand on and give it a jump test and see how it feels. If it’s spongy, I’d add a 2x4 center of the gap and that should bring you to a good place without much expense.