So it would be good if we can uncrypt them into a DOS environment (+ NTFS read driver).

If the file can be uncrypted the user could discover the missed file (warned by Windows) in some cases.

Again, Windows could inform this…

But it’s difficult to see that avast is well-designed if it can’t open the door that it has closed itself.
On boot time scanning you can send a system file to Chest. You must be able to restore a file from Chest while in boot time. If not, avast is not good.