Apart from the fact that there are incredible amounts of plywood of various kinds and thicknesses, much of the load-bearing capacity lies in the actual construction. You should make a proper design of what you have in mind so we can give tips and advice on whether it will reasonably work or not.
Thank you for all the feedback! As often, shortcuts seem to lead astray, so I'll drop that idea. I would have liked to buy a ladder, but they feel so undeservedly expensive!
However, I do have a 170x45-regel left + some solid pine floorboards. Maybe they can be used to build a staircase? Does that seem reasonable?
I did exactly like in the link, cut down a large Kallax shelf into a staircase. Just make sure that all "steps" have support underneath and aren't just resting on dowels or similar. I used pine shelving where I couldn't get the shelf's shelves to have proper support and at the top to extend the "staircase" a bit from the wall + a cozy corner for evening reading. Worked excellently, magically enough I can't find any pictures 😢 Ah, wife ftw!
Thanks for all the feedback! As often, shortcuts seem to lead astray, so I'll drop that idea. I'd like to buy a ladder, but they feel so unworthily expensive!
However, I do have a 170x45 beam left + some solid pine floorboards. Is it possible to use them to build a staircase? Does that seem reasonable?
Seems more like you are generally looking for a quick budget solution given the proposed solutions.