How can I change the default format tool in windows 7/8/10 context menu?

The Format command in Explorer is built-in and not easily modified.

One poster has deeply analyzed the problem and summarized his efforts in the post Replace Windows' drive format tool with Rufus, where he is asking for help in creating a full solution. Unfortunately, I don't see any way to finish his work.

It would have been possible to add a Rufus entry to the context-menu of all drives with a registry update such as the below .reg file (very generic and untested):

Windows Registry Editor Version 5.00

[HKEY_CLASSES_ROOT\Drive\shell\rufus]
@="Rufus on drive"

[HKEY_CLASSES_ROOT\Drive\shell\runas\command]
@="\"C:\Program Files (x86)\Rufus\Rufus.exe\" %1"

Unfortunately, this would be useless, since the Rufus Wiki post Command line arguments #111, where users ask for command-line arguments for Rufus, has this final text from the Rufus developer:

I have to stress out, commandline support is at least years away, so there's no way I'm going to go into details on how I'm planning to address something that is that far out, as things can and do change when a lot of time elapses.

Without command-line support, there is no way to pass the drive-letter to Rufus. Therefore there is no point in adding such an entry to the context-menu of Explorer, as all it would do would be to call up Rufus, just the same as calling it from the Start Menu or from a desktop icon.