Remove PhysicalDisk from Storage Pool without replacement?

Currently I'm testing the Advantages and Disadvantages of Storage Pools in my Home-Environment. The test server looks like this:

Windows Server 2012 R2 Datacenter ("Student-Edition")
2*400 GB HDD
4*1000 GB HDD
2*3000 GB HDD

First, I wanted to test a "replacement" Case: I created a storage Pool of 2*1 + 2*3 added some data to a (mirrored) virtual hard disk, and disconnected one 1 TB drive. The Pool gets reported as unhealty, and with a second Disk i was able to do the regular replacement (Attach new Physical Disk, Remove old & Rebuild)

Now I wanted to test the case, how I can rebuild full functionality, when no proper replacement-disk is available:

Therefore I created another Pool of some Harddisks, added some data (arround 200 GB), disconnected one drive and tried various ways to get back to health - nothing worked:

Using the UI it's impossible to do anything at all. After selecting "remove" on the disconnected drive, it simple keeps telling me, that there is no proper replacement disk found.

Then I followed some instructions i found elsewhere on technet:

1. mark the missing disks as "retired":
 Set-PhysicalDisk -FriendlyName <PhysicalDiskxxx> -Usage Retired

2. rebuild each of your virtual disks:

Repair-VirtualDisk -FriendlyName <Virtual Diskxxx>

3. Once everything is finished, try to remove the disk from the pool again:

 Remove-PhysicalDisk -FriendlyName <PhysicalDiskxxx>

1+2 worked fine, and I noted the disconnected disks usage dropping from ~ 30GB to 256MB

All virtual Disks reporting a "health" state now.

However, it was not possible to remove the disk: The ui told me, that it's gonna rebuild after clicking "remove" - but simply nothing happened - not after several hours (virtual Drives are "thin", so not much data to move).

Using the Powershell it keeps telling me, that theres an Issue with the "FriendlyName" Property:

I noted, that the Disk was prior shown as "PhysicalDisk-14" - but that did not change anyting.

So I followed another approach, using the following command:

It looked promising, but finally failed with "Not enough available capacity" - which is ofc. not true. (Only assigned around 1000 GB to the virtual disks, of which I used around 200)

So, the question is: How do i remove a (disconnected, retired) disk from a storage pool that has enough capacity left WITHOUT replacing the Disk immediately?