I love the packing table idea, gonegrey.
I also like a separate kitchen. I'd like a large farmhouse kitchen with a big table.
If you are going for an open plan layout, think about how you are going to use it. If you have children at home, you might want a separate living room/snug/lounge.
Will you be having visitors that you will want a sort of study/office to meet them. For example, you may have a home based business, be a piano teacher, tutor etc.
It is nice to have a buffer area between the front door and the living area. A hall or porch.
Downstairs loo is a must. OK I don't have one (yet) but in a 5 bed house you will have the space. If it's in the hall, don't have it opposite the front door.
If you are going for big windows, consider the amount of sunlight you'll get and the view. Will you appreciate a north facing view or a baking hot glass walled room. Might a view be affected in future.