Ability to relocate services to a different node

Currently services can be assigned to a node only at the time the node is added to a cluster.

The enhancement request is to allow addition or removal or a service to a node that is already part of a cluster.

As an example consider the following use case:

Consider a customer where they are running a small cluster of 3 nodes of Data/Index/Query.
As their load grows, they need to separate out Index/Query into their own nodes to ensure the performance they need.
Today they can do this by following these steps:

• Create 5 new instances
• Add 3 of them as Data nodes
• Add 2 of them as Index/Query nodes
• Rebalance, moving the entire dataset to the new nodes

This involves a lot of extra cost for the extra instances etc.
It would be better if they only had to add 2 new instances (to grow the cluster from 3 -> 5 nodes), then turn off the Index/Query services on the existing nodes, perhaps as part of the rebalance (to move the indexes across).

Maybe this use case is asking for a bit more than just turning off the service, so needs more thought.