We have an L shape dinette, often wish it was a Pullman-style. This usually happens any time it has to be made into a bed or have the table moved due to it being a very large substantially constructed table top (it'll have me fingers one day). Mostly mitigated now by using the small table top i made and the addition of a sofa bed rather than the captains chair we got shut of, so the dinette usually stays as a dinette.
I'd prefer an off-corridor bathroom, rather than the walkthough we have. It could be easily changed to this, but i'm not allowed by the powers that be (wife ).
More kitchen worktop area would be nice, but this would mean losses elsewhere or a big re-jig of oven, hob, sink, fridge etc.
Oh, and i'd swap the washing machine for a dishwasher in a heartbeat. I'm allowed to remove the washing machine, but only if i replace it with a cupboard