The subnet, security group, and availability zone really do not belong in the compute profile. They are best defined at the subnet level. One image/compute resource can be the bases for MULTIPLE instances across MULTIPLE subnets.

This might mean adding the ability for a subnet to have an additional dropdown to set the CR type so it knows what additional fields to display based on the CR in use. For an AWS selection that would mean the addition of the security group and availability zone fields. It may mean other things for other CRs.