Players have been requesting an increase for years but it seems that it's not happening. Since they doubled the slots for Storm blood, I was hoping they'd double the slots for Shadowbringers but I was sorely disappointed. I don't think there was ever an official response why they won't increase the slots anymore or if we can hope for more as technology gets better.

2 years ago, I would have said apartments and cottages had an ideal item to space ratio. In order to have the same item to space ratio, a large house would need 1600 item slots.

That being said, over the last 2 years, there was a lot of innovation with ever more complex designs among global housing decorators and at this time, I don't think 1600 would even be enough for a large. A few days ago, I visited a large house on Famfrit the interior of which was designed as a high rise apartment. The apartment took up the space of maybe a private room in. The rest of this mansion was blocked off and completely empty. Obviously the design was gorgeous but my heart kind of bleeds for all that unused space. At that level of complexity a large house would need 6400 item slots.