Hello Richard.

Yes, it is possible. You can use RecycledAttribute for new Entity and specify old full name of Entity.

For example, you have old entity

namespace MyApplication.Model
{
  [HierarchyRoot]
  public class SomeOldEntity
  {
   // Fields specification
  }
}

And you rename SomeOldEntity with SomeNewEntity

namespace MyApplication.Model
{
  [HierarchyRoot]
  [Recycled("MyApplication.Model.SomeOldEntity")]
  public class SomeRenamedEntity
  {
   // Fields specification
  }
}

It is simplest way to rename some enity. And you should build domain in Preform or PerformeSafely upgrade mode.

Another one way to change model its implement your own Upgrade handler. Upgrade handler is class responsible for upgrade of persistent classes from one assembly. It must be inherited from UpgradeHandler or implement IUpgradeHandler interface, it also must have a parameterless constructor. Each assembly with persistent model should contain exactly one upgrade handler class, it will be automatically found when schema is being upgraded. UpgradeHandler class contains a set of methods and properties that can be overridden for customizing schema upgrade process. For example,

public class Upgrader : UpgradeHandler
{
  protected override void AddUpgradeHints(Xtensive.Collections.ISet<upgradehint> hints)
  {
    //rename entity
    hints.Add(new RenameTypeHint("MyProduct.Model.Customer", typeof (Person)));
    //rename field of entity
    hints.Add(new RenameFieldHint(typeof (Person), "Name", "FullName"));
  }
}

You should read documentation about upgrade for DO-4.6 and for DO-5.0 Beta.