Paul, it's simply the Tactician head on the
E1 (18350) LF body with an
EDCLB E2T tailcap.
The challenge with trying to Lego the Tactician head is that the threads are machined differently than the typical E-series body. Specifically (1) the threaded area is slightly longer and (2) the O-ring is not located at the bottom of the threads - it's moved slightly forward. So while I can get the Tactician head to work on the Lego as shown in the photo, it's not optimal requiring a hard twist of the head to engage full power.
To make this Lego viable the front threads of the LF E1 body would need to be extended and machined like those on the Tactician body. It may not be out of the question to have some made that way, but it would be a considerable investment and would require some committed buyers.
That said it's a very impressive Lego, one I definitely would carry myself!