I think you would achieve the best results by putting the plants in larger (1-2 gallon - you could even do 3 gallon if you wish) containers and a mix of coarse sand, pine bark, and sphagnum peat, powdered sulfur. The key to using this heavy mix is going to be in the fact that you'll partially bury them, which turns them into raised beds, hydrologically speaking. You can use heavier, more water retentive soils and much larger volumes of soil when you have the entire earth as your wick. ;o)

It may be necessary to lift & rotate the plants yearly because the roots will grow through the drain holes in the pot & anchor the plant. Plus, doing so helps you maintain a low enough pH (inside the container) so (excessive) Ca uptake isn't a problem. Blueberries like a lower pH because they have a problem limiting their Ca uptake. You can leave the plants in the ground all year long, unless you start seeing pH issues.

Fertilizers that use urea or ammonium sulfate as the N source are best for blueberries in containers, but be sure to withhold them when SOIL temps are below 55* to avoid ammonium toxicity.

Al