If your friend wants to play Sallies, he wants to use Vulkan. Period. His benefits to Melta are necessary to make Salamanders work. Period.
Sorry, not optional... period.
But. Having the model, it would be slightly tricky, but not obscenely hard to remove the BA iconography from the Deathstorm Captain. There are several small blood drops to shave flat, nice and easy. His right leg has a large blood drop with wings thing going on, as long as you remove it before assembly it should be easy-ish. Either have something to replace it with, or be careful to maintain a rounded shape.
The two hardest parts to deal with, if you're a perfectionist, would be a blood drop centre of his chest, between wings. You could probably shave it flat and work it into a headless Aquila sort of thing. The other tricky part would be the "wing" counterweight on the Thunder hammer. If you had some Salamander bits from a Drop Pod [maybe?] that had the fiery bit behind the salamander skull... that would look really good. I removed the head, replaced with an Axe as I made a Termie-Librarian, but I think the Sally skull might fit in the face of the hammer, which would again really emphasize the Sally-ness.
But really. You need Vulkan first and foremost, and he's a beautiful model. Essentially a better version of what you're trying to do anyway.
