If you lack the domain knowledge, then you lack the skills and experience to make it happen. Then you might probably also lack the awareness and the business knowledge against what you are proposing, meaning you probably shouldn't propose it in the first place.
Well if the person lacks the domain knowledge of television engineering, but not the domain knowledge of IT, he certainly would not fail in a pure IT department if he has suceeded as an IT guy reporting to someone in television engineering. If the person making the proposal has basic understanding the television engineering field, domain expertise in IT, but lacks the domain knowledge of business, then maybe he just needs a starting point to know what questions the business stakeholders will ask. Once this person knows what questions a business stakeholder will ask to see if a proposal makes sense. he can do his own research to put forth a proposal.
Going back to my original example, he knows a separate IT department benefits him, or at least thinks he does. He knows he has to frame it in terms of how it benefits the business. So he wants to know what he doesn't know so he can form that argument.