For example, would "I want to know of good first hand sources and academic texts about the Templars military tactics" be on or off topic?
What if instead of banning such questions we created a special tag for them, similar to Tex.SX's 'Community Wiki' 'big-list' tags? I can see the value in such answers, as starting research in a new area can be very daunting, particularly with a broad topic or one with answers scattered through books on more general topics. Also when I come to history.SX I'm not likely to have an identical question as someone else, but if I have a similar one then the list of references could be very useful.
For example, I'm starting an essay on German Rearmament. I don't want people to give me information on my essay topic outright, but I would love to have some of the more knowledgeable people point me to where to find books on it, as such topics are scattered; I've got books on the end of the Wimer republic, the start of WWII, military history and the road to total war. I'm positive I'm missing good sources, and have a number of chaff book sin my pile, and being able to ask for help would be really useful, as well as beneficial to anyone else working on the same topic.
I'm having trouble finding examples right now, but Naming LaTeX Files is a clear example of a clear, but open-ended, question, as is What are the finishing touches you put to a document?
I think having them as questions is much more useful then in chat, as it is far easier to search for questions on the same/similar topics when a new person comes along then it is in chat. Chat also has the risk of no one available to help, especially as we grow, then answers do.
Finally if I'm out and about and see a question asking about, say, the British Army leading up to WWI, I can say 'Oh hey, I just wrote an essay on that, I'll grab my sources list for them when I get some time' -I'm not going to do that if they ask in chat, and I don't see them online again.
I would say that we need to restrict such questions to narrow topics: "I'm looking for sources on the British Army in the years leading up to WWI" or "1850-1914" for example, not "What are a list of good books on the British Army?"
These types of questions should be strictly off-topic. These are what I would consider list questions. You'll get a bunch of one-line answers and I don't think they'd really add value to the site.
This question could be rewritten as "What were the Templar's military tactics?" and would be on-topic (well, it might be a bit too broad).
I think this site will get a pretty alive chat for side-reasoning/discussion where such reference/keyword questions can be asked. Also Wikipedia gives out alot literature links for every topic.
But too much of those questions would likely corrupt the tag system of "real" historical questions.