I think you've got the right idea.
Your framing will be the base for the cabinets so frame away, put the cabinets in there and skin it.
Make sure and have a nice sturdy top with an easy to clean surface.
I've got my granddad's old bar in my house. I'm building the chest freezer kegorator to match the height of it.
Due to the design of the bar and the fact that I want to use his old bar, I'm going to put cabinets and a sink behind the bar.