I thought the egg-white texture was done in the DTE and was suitably impressed since it completely baffles me.  I would use metaballs just like you.  I like the grave idea.

Originalmoron did heat shimmer on a render of his new ship and said,

"That is post work. Draw the outlines of the heat comming from the jets with the freehand selection tool. Sett to feather about 26. Then just a gausien blur. Its simpler then it sounds :)  And that was in paint shop pro."

Maybe some version of this can be used to make it.