Allow the inside of a house, apartment, fc room to be a selected design.

For example, someone might not care to have a basement but might want a bigger main room.

Imagine if a small house could have simply one big room like the large house's basement. It is a shame to get space like that requires a large house. For some, just that basement is all they really want.

Similar, people unlucky to get a house might enjoy being able to make their apartment have a downstairs like small houses do.

Infact, someone with a large might not like the inside design of larges and might opt for a medium inside design rather than what large has now. I know some who dislike the large house version of an attic.

I would go further to say, in a world of magic, there is no reason a small plot cannot look like a large inside.
Would this anger people with large plots or deter buying them if a small can have the same inside?
No.
Larges are coveted simply because they are super rare. They also have the biggest outside space. They are essentially an item of status for a char or fc.

Ex: allowing an apartment to have a small house inside doesn't destroy the desire for a small house.
Why?
Point of a house is visibility. People can run around and see it. Apartments lose this.
Fc will always want a house.
Most hang around the outisde of a house even, something apartment doesn't have.

However, if you let apartments change the layout and small houses opt for a bigger inside, housing would be less of a pain than it is now.

At least somone who didn't get a house could have the feel of a house in an apartment instead of a tiny one room thing.

Someone with a small who didn't get a med could rearrange the inside, etc.

And ofc, allow gardening indoors.