The requirements as taken from: HAC-4062:

 
This feature will allow customers to select their own sizing (within our provided constraints such as minimums, maximums) for the disk volumes of their worker machinepool nodes for ROSA HCP.

Customers will need the option to select the sizing for the default machinepool at cluster install-time.

Customers will need the option to select the sizing for the new day2 machinepools (after the cluster is installed).

This feature will not allow the resizing of existing machinepool node volumes.

Design doc from ROSA Classic: https://docs.google.com/document/d/1jgHGMqEXiJJVdkF1riM7YxG4oJR4Zv-1-4bHDc4jeEE/edit?usp=sharing