The BFG exists in several versions:

The original from Doom 1993 is just a rectantular box with a weird handle, the sides of the box is covered with techno pixelart, but nothing striking.

The Doom 64 version is very similar to the 1993 version.

The BFG in Doom 3 has a profile of a weird space potato: https://doom.fandom.com/wiki/BFG9000/Doom_3?file=BFG9000-BP.jpg

The ingame model is more like a rectantular box, but with an updated case: https://doom.fandom.com/wiki/BFG9000/Doom_3?file=Bfg3

In Doom 2016 is has a better styling, with an actual grip, it now actually looks like a gun!

In Doom Eternal it looks great, if a bit generic, but not bad.

The BFG does exist in Quake II and Quake 3 Arena, but the design is just terrible.

So while I like your enthusiasm, I don’t share your oppinion on the design of the BFG series.