I see a lot of ideas here, but those are wished. I wish to build a stone house too!

But let's be realistic: what were the two most successful games from Stronghold series..? Of course: Stronghold 1 and Stronghold Crusader! And none of future games didn't make it beat one of those two. People still play them, and enjoy those games more than playing SH 2, SH L, and even SH 3! Of course, SH 3 is a new game, and there is a lot to be fixed...
But what is the most important in those two games is that they are not just castle building game: there you have castle building, running economy (which is not too complicated), you don't have rats, gong criminals, candles and other things. You have food, inns, weapon production... Most of players would be pleased to see a new Stronghold Crusader game, with only few modifications, and I hope it would not be too hard for FireFly, and it would also bring you money.
What would these few things be..? For example,
larger maps! 800x800 for example... That would be great in skirmish! Also, many would like to see more options for
resolution. Most of players who play SH:C play it on new monitors, and picture is stretched, that would also be "fixed". Maybe some more options in
map editor... You could publish it just like Stronghold Extreme, but without those stones falling from the sky, and other powers... Just the old good Stronghold Crusader with few modifications...
I didn't write here all my ideas, I could do that later, but this is not only my opinion, this is what most of players think...