That second solution sounds like a really good one. I think I could actually go with a little smaller dimensions that way when it doesn't have to support itself in the same way.
There has been some progress in the last days.
I put in four of these into the front part of the platform. What are they called in english?
I put them in to be able to put these in to hang the platform as a table
I forgot to take pics of the table side of the platform but I stained it black and put 3 or 4 layers of clearcoat.
Got the platform painted, covered in carpet and finished
Here you can see how I meant the front seat need to sit. Little easier to show than explain.
Had to test it
It feels like a lot more room than I expected
Started on the slide out
And once again I realized, calculating and building stuff when you're tired will make you redo some of the things. The slide was a perfect fit if it wasn't for the slide fittings.
So had to make some cuts and reglue the lower sides to make it fit into the cabinet.
Getting closer!