Whilst I understand your limited space, I received some very good advice 4 years ago. That was to purchase a separate thicknesseser and planer because you will spend a lot of time changing operation modes on a combined machine. With two separate machines you can plane one side, thickness the piece and then back on the planer, joint it for a panel, either singly or in batches. Think of the time lost and frustration in changing modes during this processing.
Also depending on the manufacturer, you may not pay a significant amount more for the convenience of separate machines.