No - although I got fairly close last year when overhauling the rear suspension, so I took a good look at what it would take if this was necessary once I'd got into the task. (In the end, the only parts that were really worn were the lower arm balljoint and the wishbone outer bush. I changed both top arms and the balljoint while the car was in the air).

To your point, the two inner bushes can be removed from the rear lower arm once you have the arm off the car, and the bushes replaced: my local parts stores hold both bushes in stock from various manufacturers. You don't need to buy another lower arm but you should get access to a press as I would imagine they will be fun to remove and replace without.