Bought a hutch - need advise

I just bought this hutch for my 3 rabbits but haven't assembled it yet
https://www.amazon.com/gp/product/B003TOQ1XO/?tag=skimlinks_replacement-20
They will not spend there 24 hours a day, so space shouldn't be a concern.

Its constructed of pine wood that is treated for outdoor use.
Should I additionally buy anything to treat the outside of the hutch? It will be used outside.
On the second floor there are 2 pull out trays. I guess I need to build 2 frames to insert on top of trays so that pee and poo falls thru the mesh? What mesh should I use for this purpose? Trays are supported by wooden strips underneath, but I am concerned that the "second floor" won't be strong enough for my 3 large bunnies. Do you think I could reinforce the second floor?

The ramp is too narrow... will need to use something underneath it. Any idea what I could use for a wider ramp?

How would you organize the second floor, I mean what should I put on the floor there? I plan to have a rug, litter box and food bowls on the ground floor (if we decide to keep it on cement) but I am confused what to do on the second...

I will certainly have more questions as we assemble it

Thanks!

the hutch

I don't like mesh in rabbit cages, personally, but I'd use a narrower holed mesh if possible. You can support the second floor with carefully placed wooden dowels, which aren't too expensive.

My rabbits have a homemade multilevel cage. We put all the 'gross' stuff on the bottom floor- litterbox, hay, food, etc. This one has vinyl for easy clean up. On the second and third floors (ours are lined with carpet) they have a few memory foam pads (to protect from pododermatitis), a few toys, a little hidey hole, and that's about it. Most of their chew toys end up on the second floor and the third floor is more for sleeping after they redecorate.

thank you RavenousDragon.
Do your rabbits always go to the first floor when they need to use litter box?
I think this mesh is fine.

One ALWAYS goes to the bottom floor to use the litterbox, I can count on it. The other one always urinates in her box, but sometimes, she leaves a few feces on the top two floors (it's super easy to clean up, though, since it's only a few). But part of that, depends on the individual rabbit. If yours are really good at using the box when they are out and about, they will probably be good about using it in the cage too.

today we assembled the hutch.
I will need to replace the ramp as there is no way my large rabbits can use such a narrow one
The second floor most likely won't stay in place under their weight. So reinforcing it would need to be done.