A) Quest huts.
I really like the progression of quest huts, from some small Inns to Witch Huts to Wizard Towers. Of course I wish there were even more of these different kinds of quest locations (Magical Groves, Feuding camps/villages..), but the current setup is already great.
I like the progression, but there is clutter still. For example, I can often see 2 inns that offer level 1 quests. I go to one of them, get a quest and finish it. I go to the second inn, and it tells me there are no quests at this location. Well, why is it there then? Each location should have a quest to give at all times, else it shouldn't clutter the map. Repeating quests is not a bad thing, and certainly better than keeping these now-useless tiles on the map forever.
I think the most common sense way is to have a quest attached to each tile at spawn. For example, let's say there are 10 level 1 quests. When the game spawns an Inn, it randomly picks one of the 10 quests to assign to it. If another Inn ends up picking the same quests, the game doesn't care because they're different Inns. Completing the quest from one Inn does not leave the other one empty.
B ) Quest variety.
Escorting, finding an item, fighting a battle. The variety is enough in the lower level quets, but towards the higher level quests I would like a bit more variety. I'll adress this in part C.
Not all the possibilities of variety are explored, but they should be. Most quests only have one step, which is okay for level 1s but should increase in amount of steps as the levels climb. There's no reason not to have a quest that starts because a Bone Ogre has a %chance to drop an "Ogre Tooth", which starts a quest by telling you the tooth looks interesting somehow and maybe you should take it to someone to look at. So, you take it to a witch who claims she can make a "charm" out of it, but to do so she requires a few more teeth and helpfully points you to an Ogre Den. You go there, kill the ogres, loot a few more teeth. Bring them back, and she makes you a necklace that you can equip as an accessory.
Or a simpler quest, you kill a wolf and get its hide, which starts a quest saying "If you get 4 more hides you can bring it to a leatherworker who can make you a suit of armor". So, you find more wolves in the wild, loot their hides, take it to a special "Leatherworker Shop" tile, who then asks for some gold and materials and makes you a nice suit of leather armor.
It's boring when every quest creates a tile for you to go to. These kinds of quests reward exploration and make it more engaging. You don't know if you'll find a wolf to loot a hide. But if you do, you've got the quest. Then you just need to find the leatherworker, and that tile doesn't "spawn" because you got the quest. It's created on map start, and you just have to find it (if you find it and don't have the quest, it can just give you a message saying the leatherworker takes animal hides and turns them into armor, so you now know you can look for animals you can skin). Only having quests that start on a specific tile and end on a specific tile created just for that one particular quest is not good variety.
C) Quest level progression.
The higher level quests feel quite a bit the same as the lower level ones. It would be nice if high level quests actually were more demanding, more difficult (other than having higher level monsters) and more exciting. Some quest types that are missing that would be really cool would be:
1) Kill a certain NPC (that you don't control). Whether the NPC is neutral or owned by another player doesn't matter. You need to kill it to complete the quest - this might mean having to declare war on some kingdom or using diplomacy to make the other kingdom to give you the NPC on a silver platter. Wouldn't it be kind of cool to negotiate essentially the price on hanging of an NPC with your opponent? Would add a dimension to diplomacy, too.
2) Destroy a city / steal something from it. The truly high level quests should have really difficult dynamic tasks. Destroying a certain major / minor faction city would be difficult enough to make adventuring really interesting. Works the other way around - for no apparent reason a group of heroes might attack your city, just because some quest happened to set your city as a target. In my opinion winning the game with a master quest should require you to do some quests like this first.
I mentioned it above, but the higher level quests just need more stuff for you to do during the quest, multiple steps needed to accomplish. Maybe a level 1 quest for "Bandits raiding a workshop" just has you go there and kill them. But maybe the level 3 version of the quest has you go there, find the bandits long gone but you pick up their trail and follow them to camp. You go to the camp and the bandits attack you, but you find out that a band of Darklings raided the Bandits and made off with everything. So now you go find them, and finally recover the materials for the quest giver.
D) Quest plot lines.
It would be nice to have some level 1 quest continue from a level 2 quest hut, eventually leading to a top level quets that gives a big reward. If all the quests are completely independent of each other, it'll never feel as grand as if there are some longer running plot lines.
Most definitely. A big quest arc that spans across all quest levels can be made very awesome, and very rich.
E) Quest prerequisites.
Currently, all you need to do is research higher quest levels to be able to do higher level quests. Here I think it would be good to incorporate something from RPGs, gateway quests. What I mean is having a level 1 quest that you have to complete before you have access to level 2 quests - this would be in addition to researching the required tech. Perhaps a quest you get from an Inn that gets you acquainted with the Witches of the world, thus allowing you to get quests from witch huts.
I like this idea. I would even like if this kind of quest actually unlocked the research tech. Using your example, you wouldn't be able to research level 2 questing at all until you did the quest from the inn to meet a witch (and do a short intro quest for the witch). I don't think this is likely, though. Your idea might be, if they make it so that a quest can have another quest as a prereq, then you simply add this "level 2 intro quest" to the prereq list of every level 2 quest.
G) Quest hut lifespan.
Another thing that would make the world seem more of a world instead of a grid of tiles would be to make the quest huts at least partially permanent, offering multiple quests each. A Wizard Tower wouldn't go anywhere once you complete the quest. Instead, after some 20 turns from completing the last quest it would have a new one. Every now and then a quest hut could vanish (in my head it would be best if it was displayed as 'worn out' for some turns to indicate that it's disappearing soon), and soon a new one would spawn somewhere else. When a quest hut vanishes it would be really cool to have a goodie hut of the same level in its place, like "Tower Ruins" from a wizard tower.
I've thought about this and personally I sort of like it, but the problem with the idea is the randomness of the map. Unless the map generation can guarantee relatively fair access to the quests for each player, it might not always be fun. Maybe your start doesn't have any marshes anywhere close. Especially if you combine it with your suggestion about quests serving as a pre-req to a new quest level, it would kind of suck if you can't get the prereq quest because the quest hut isn't anywhere near you and you have to wait for a lucky re-spawn.