Is drainage necessary under the entrance platform?

I also recommended to the TE to make the pedestal from one piece. It is not really more expensive than pieces measuring 50x50.

Attached is a picture during our winter snow disaster

Well, and still you have the connection joint there - in your case it is also not yet covered.

this joint is sealed with silicone. you just have to redo it every few years.

it's something completely different whether you do this one joint with silicone (which you have to do anyway because of elasticity) or whether you have to make numerous panels properly watertight (or get rid of the water). the whole thing was done by the specialist company, who probably also knew how to do it.

Exactly, you have to do that too - if there is [Putz], it gets more complicated...

A lot is possible as long as you are aware of the potential risks.