Destructive XML is completely supported in salesforce dx. All you need is a directory where you will place a package.xml file and a destructiveChanges.xml file.
destructiveChanges.xml will be an XML with all the components you want to delete. Check the documentation here
where destructive is a folder with package.xml and destructiveChanges.xml
sfdx force:mdapi:deploy -d destructive -u <username> -w -1
You can perform a deployment that specifies components to delete in destructiveChanges.xml and components to add or update in package.xml. The process is the same as with performing a delete-only deployment except that package.xml contains the components to add or update.
By default, deletions are processed before component additions.
In API version 33.0 and later, you can specify components to be deleted before and after component additions. The process is the same as with performing a delete-only deployment except that the name of the deletion manifest file is different.
To delete components before adding or updating other components, create a manifest file that’s named destructiveChangesPre.xml and include the components to delete.
To delete components after adding or updating other components, create a manifest file that’s named destructiveChangesPost.xml and include the components to delete.
The ability to specify when deletions are processed is useful when you’re deleting components with dependencies.
On the Rename of Metadata ,only Metadata that supports CRUD based (You can use Metadata WSDL and check if components extend tns:Metadata) are supported in Metadata.Rename()
Since the SFDX CLI is based on jsforce and jsforce has excellent support for the Metadata API you can easily build a custom plugin for the salesforce dx cli if you want to use the rename command .
I just build one and you can install it using below
sfdx plugins:install mo-dx-plugin
Once you have it installed you can use below command,
sfdx metadata:rename --metadatatype CustomObject --oldfullname object1__c --newfullname objectnew__c