You are lucky ! We are lucky to we have a house what we love, i mean when i move i would like to pick it up and plant it somewhere else. But when i could design from scratch !! i know exactly what i would like different. No room shuld be too small on no wall for a big double bed, in the bathrom i want 2 sinks a stap in shower and a bath a steam room ans a sauna. In every sleeping room there needs to be the possobillity for running water . And my kitchen has to be big a square so i can put my table in the middle.
I think that when you start with the things you do not like in your own house, you know where to start designing a new .... Succes and keep us posted