If those six copies are actually from three different transfers, you're in luck already. There may be just two different transfers. To use that median/average magic properly you'd have to use image registration technique first, which also takes a lot of dedication. The result could be easily better than the NTSC DVD yes, but it doesn't contradict with what I have said: it'd still be DVD quality.

Noone can tell how the BD would turn out. But having a flawed, high resolution BD version to work with is a much better situation than having only SD materials.