Update to workaround,
Have not heard much back from Avast on this one but the latest update to a workaround is tolerable if you desire a drive letter.
What one needs to do is mount the drive as a volume instead of a letter then in the registry port that folder to a letter.
(1) Create empty folder, Suggest using drive label.
(2) In diskmgmt.msc select drive you want to mount to a folder, Select "Change driver letter and paths for "Label_Name", "Add", "Mount in the following empty NTFS folder", Select path and click OK. That will show the drive as a folder.
(3) Now to show as a drive you need to go into the registry and create a new string value with the letter of the drive you want that folder to be, In my case D:
Now the value in my case is "\\??\\E:\\Win" and on reboot you will see a D: drive and Avast quarantine restore works perfect with this addition.
.reg file looks like this for my case.
Windows Registry Editor Version 5.00
[HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\Session Manager\DOS Devices]
"D:"="\\??\\E:\\Win"