Hi, I spent a couple of years pursuing this dream. I wanted to be the first to produce a set of plastic WW1 Anzacs, along with Turks, to recognise the battle of Galipolli in 1915. I went to various Australian mold makers but the cost was way too much or they had no idea. The only feasible thing was doing it through China. I had quotes for 8 figure molds for $5,000 - but these were from the company that make BMC - great for kids but not up to standard for my purposes. In the end I brought out a range of Metal figures but despite some success, it was a niche market in a niche market and I wound it up a year or so ago.
My advice is to seek out a proven manufacturer, like TSSD and do a deal with them. These days the sculpting needs to be excellent, so get on to someone who knows what they're doing. (I had a fantastic sculptor but he was very hard to direct, he made my plans do-able but his lack of reliabity also ultimately extinguished them). Cost per figure may well be $1,000 though. I also think it best to go with a popular range but with something new. For instance WW2 Germans - but a recon set, which hasn't been done in plastic yet. There could be a couple of motorcycles with side cars, with riders (tricky poses though) and scouts etc.
I had a list of figures that I was going to do but it's all done with now. I'm particularly sad I didn't get the range of dwarves/elves/orcy (werebeasty at least) things up. I'd have cleaned up when Lord of the Rings came out. No one has ever done these properly in plastic (at least in a toy soldier sense). I pictured them selling in book stores too next to the books by Eddings, Feist, Gemmell, Jordan and so on.
Oh well, such is life......