I like the idea of the tall raised beds myself, for the reasons that you stated, but would be inclined to consider something like these metal modular beds rather than something made of concrete:
https://vegogarden.com/product...
I agree with other replies about the 3x3' size, especially with the concrete wall those are going to waste quite a bit of space. Raised beds that are 2 or 3 feet wide but longer would be easy to reach across and provide plenty of room for growing most garden plants.