I agree this is the EB's biggest missing feature. I do it by having a second environment running the same web app. Before deploying I add nodes from this 'rese

I agree this is the EB's biggest missing feature. I do it by having a second environment running the same web app. Before deploying I add nodes from this 'reserve' env to the ELB of the main env, and remove all the nodes-to-be-deployed from the main load balancer. Then I deploy the app. When deploy is complete and prod nodes are ready I add them back to the ELB and remove the reserve nodes. The deployment is seamless but this is not a convenient trick - it required a fair bit of custom scripting... Luckily AWS provides great APIs to make all this stuff possible.