You'd need to see how they are with the ramps. Years ago my dad made me a cage for our 4 sows (2 pairs of mum&daughter pigs) and they used the ramps happily. They were carpeted with a side so it was like going through a tunnel.
My boars have a wide shallow carpeted ramp to the lid of their haybox. If DD puts them on the lid they'll run down the ramp as fast as their hungry little legs will carry them. But not 'up' the ramp. Too lazy <<sigh>>
It means they lose the use of half the cage if they would use the ramp (or make you carry them up and down)
I like the fact the doors have proper bolts that's important fox proofing.
Have you boars or sows? Fine for sows. And you've already said piggies sleep in at night.
If you have boars what will you do if the ground is too wet to put the ramp down? Having said that my boys lived together for almost 4 years in a 3 foot hutch. When I sadly had to separate them, neither liked the 5 foot hutch I'd bought.
Guineapigs don't dig but if you have a run attached to a hutch make sure the ground is really level. Look for even tiny gaps and block up on the outside with bricks. You would surprised how small a gap even a fat piggie can squeeze through. This happened to us when when Fatimus girlie wanted to meet up with freeranging old boar . She got out of a triangle pointed run.
I would say look around at independant pet shops. That's where my boar hutch came from nice and sturdy. The girls sleep in a P@H hutch, the floor bounces. We did get a bargain from ebay carpenter made run with attached 'summer house'. Elderly couple had commissioned it but due to ill health realised keeping piggies would to too much for them.
Have lovely image of piggies with hard hats and shovels digging their way out .
They won't try and dig out - GP's seem to be fairly lazy. Two storey one sounds good - just make sure the ramp isn't too steep (no danger of them falling off) as piggies aren't really built for climbing.
What kind of cage do you have indoors? I'm thinking of a new one for my boys and am trying to find something a bit nicer to look at than the standard plastic ones.
We just need a new one - ours was basic and not very waterproof anymore. We do a mixture of indoor and outdoor, they sleep inside all year round and kept indoors when weather like today! Otherwise they are outside in the hutch. Just thinking about a two story one with access to grass at the bottom. Is that a good idea? Will they dig out a tunnel???