Areas of value when building

I'm sure others constructing seek similar answers, but for those of you who have been down this path or who are better experienced, I would be keen to get some healthy debate on the following considerations and how they may affect either 1) Rental return/appeal or 2) Future resale value.

I'll get the ball rolling with a few on the back of my mind currently, feel free to add anything else you think is important (beyond what a standard home build would usually come with, i.e. has to be added in or costed ).

1) Raised Ceilings.

In my situation (to add context) the promo (built into the house price i'm sure anyway) raises 2 courses so I'm 30c throughout for only $990 more. But to go up 1 course to 31courses we're talking $4,500~. I don't think it'll add any rental return value, an unquantifiable immaterial rental appeal perhaps. But for resale value - thoughts? Or between 30/31c you'd leave it at 30?

2) Elevation

Much debate here. My basic elevation of $900 for a basic blade wall and pier out the front would have to be upgraded to a total of $2,700 to go with a (looks basic) portico.

Curious to hear thoughts. I assume again no rental return on this one but not sure if $2-5k on elevation will add to resale value in 5, 10 years time if you need to.

3) Double vanity basins, double showers (or at least full length shower with only one shower head/tapware) etc - another area of hot contest.

For $500-600 you can upgrade the shower to double, and another $1k or so gets you usually a lengthened, 2m vanity with double basin and cabinetry. Curious to hear thoughts.

4) Adding in gas bayonets - internal and external.

External- I say yes, for BBQ's etc. Internal - real estate agents still go on about this for maximising rental appeal but builders now argue you can just use electric heaters indoor so the days of gas are gone?

5) Little extras i.e. Cold water tap for your fridge recess, stone benchtops in your secondary areas i.e. ensuite, secondary bathrooms

One interesting one is the use of His/Her wardrobes and the like? Unnecessary cost addition, or a valuable low cost value addding idea in your opinion?

6) Room sizes

Personally felt like 12m2 for secondary bedrooms were reasonable, with robes excluded or in the external wall cavity to ensure a nice square, usably 12m2. I've found those rooms with 9-12m2 inclusive of robes the internal usable space felt quite limited.

Master bedrooms I'd say 16m2 minimum, the missus argues 20m2 haha.

I assume besides the kitchen/open living area this is one of the top areas any renter or potential buyer in the future will assess.... haven't got an opinion on theatre or study rooms, they generally seem to be quite small per my plans so far....