Yeah. If he was willing to try stuff like transforming her into something else that'd provide regeneration he could probably have gotten her turned into a red court vampire by now. Or paid for healing that comes with a nasty catch from someone else for that matter.Would be better to just restore her to health rather than try to upgrade or minionify her. She was a young child when she was originally injured but is well into adulthood now, with most of her life spent in a coma. It would be good enough just to wake her up, but if we could also restore the lost years, Marcone would owe us big.
The Shroud didn't work because it doesn't really have innate magical powers, not in that way. In the DF setting, however, it does serve as an immensely powerful focal object for the Faith of a significant chunk of humanity, so that gives it a lot of juice in certain circumstances.
Offering to make her into a monster, cyborg, or minion/hostage would probably convince him to send us home with a firm no and complementary car bomb.