No one here ever mentioned putting up billboards, never mind in wilderness.
My suggestion is only to add some additional signage to the 5 problem trail-heads, already covered by the WMNF trail steward program. Those 5 trail-heads, already have a good sized Kiosks. A separate and easily smaller one dedicated to safety and navigation, could be helpful. QR codes could possibly be helpful but it depends on the type. The information you'd like to be able to access with one, would require a Dynamic QR Code and that would require internet service. For just text, and a URL web link to more info., would only need to be a Static QR Code and no internet service is required. However, if you got a URL to a web link such as a map, weather, etc. from it, you will need internet service to open it. Relying on a good internet connection, is not good idea. It is pretty clear, that the US Forest Service and or the NH Fish & Game Dept., do not want hikers to relay on electronics to stay out of trouble.