WitP AE would probably fall into your criteria but that seems to be doing pretty well with an active forum. Although I have not posted there in some time. I actually wrote an article about the game for the Wargamer called 'Queen of the Pacific'. Although I have no idea of sales numbers.
I would agree that less people would buy a game like that, but as far as I know, many people are still buying both the board game and computer version of World in Flames. So I do think there is a decent market for a larger scale map WWII game, Europe, Pacific, or both. However, would the profit made offset the effort involved?
In both AE and WiF, AE was community made so making money was not as important as making the game better. Steve, the only developer for the computer version for WiF is doing this because of his love of the game. While I am sure making some money off his efforts is nice, I'm also sure he is not living off that income.
So if you want to do game design full time and live off the proceeds, then games that you think will sell the best are the ones you need to do. Which leaves people like me complaining about the lack of larger map games lol.
For reference, every so often on the AE forums someone asks about 'someone' making a War in the Pacific 2 game. The best estimate that some of the people that developed the AE version of WitP came up with was around 200-300K USD. It could go higher depending on 'feature creep' and other factors. If we use 400K as a worst case number, which is about a 35% project buffer, and the game sells at $100 (to make the math easy , that means the game would need to sell 4,000 copies to break even or make a small profit. Needless to say more copies would need to be sold if the pricing was less than $100. Of course if 10K people would buy the game then it would be a slam dunk to make it lol.
But one more thing to consider is that you would not have that 4k of people (or 10K) buying the game in a short period of time. It could take months, if not years, to reach that break even point. If you want to make some extra cash and you don't care how long it takes, then you would be fine with waiting. Otherwise most of us cannot afford (or do not want to) to have to wait like that.
So we will have to wait for someone like the developer of WiF to come along and do this as a labor of love versus wanting to make a reasonable amount of money in a reasonable amount of time.
And that is the reason 2 by 3 has not done this yet Not to mention I'm sure they are knee deep in Steel Panthers 2, War in the East 2.0, plus some things I'm sure we do not know about.