Canopy usage - Is the idea feasible in this way?

Hello, I would appreciate ideas and tips on the following: We have a small canopy above the ground floor that forms a sort of basin (apparently, according to the construction company, it couldn't be realized any other way), meaning it is not closed on top, but an open basin with a tar mat on the floor and an opening for water drainage. The dimensions of this empty space on the roof are approximately 3.50x1.50x80cm. It is not usable as a balcony, at least not officially. Quite a few people have stood on it and jumped on it (= construction manager), but officially it is not permitted in the documents. A balcony simply wouldn't make sense there in terms of the view. This area is currently accessed through a normal window on the upper floor (later a children's room). Question: What should we do with it, how can we use it "nicely"? Our first idea was greenery, so pouring in lots of soil, etc., a flower meadow on top, done. The problem might be a) the load (we fear that the roof might eventually become too heavy with wet soil), b) possible mold/other infestation without noticing it in time, and c) the cumbersome maintenance of the meadow. So, new plan: fill everything with foam or similar, on top a nice artificial turf or similar and then you could basically open a flower stick area, meaning inserting various sticks made of metal/wood (those things that are actually used as decoration in flower beds), which are long enough to be seen from the street below standing there. The question would be whether foam would be firm enough to hold the sticks, and whether the foam might also soak up too much water and thus hinder water drainage. What do you think? Maybe there are also completely different ideas...?

Do you have a photo of the entrance?

Have these photos... I hope the interesting spots can be seen on them. By the way, a slight change in the numbers after remeasuring: the dimensions are 3.48 m x 1.48 m x 0.62 cm. We would not want to fill the whole thing up to the very top, so only up to about 0.40 cm in height.

I wouldn't do anything at all there. It would always hold the rainwater on top..., can only cause trouble eventually [emoji853]

Palms in pots;
Roses in pots,
It gets a bit more difficult with watering, but if the palms are tall enough you can see them from below and above - could be pretty :)

Hmm, potted plants would indeed solve the problem with rainwater or at least greatly reduce it... sounds not bad. The roof is on the east side and is of course also affected by the shading of surrounding houses. So it would have to be something that can also handle shade...?!

My husband had the idea in the meantime to fill most of the cavity with light foam and only apply a thin layer of soil on top, similar to a flat roof greening. Then it shouldn't get too heavy at least.

@ ypg: Would there be a difference between our roof and a garage roof, which can also be greened etc.?