I haven't read through all 23 pages of this thread, so the idea may have been posted already. If so, I apologise.
My idea is about the technology research. Since this game will be much more freeform than, say, HoI (although maybe not as much as EU3), various technological paths should be made available. Will you invest in developing steam technology or go with the new internal combustion engines? Will you stick with DC or go for AC? The scientific debates were one of the driving forces of the 19th century, and representing them as a widely branched technology tree might be a good idea.
My idea is about the technology research. Since this game will be much more freeform than, say, HoI (although maybe not as much as EU3), various technological paths should be made available. Will you invest in developing steam technology or go with the new internal combustion engines? Will you stick with DC or go for AC? The scientific debates were one of the driving forces of the 19th century, and representing them as a widely branched technology tree might be a good idea.