The key to making the world of FE come alive are, in my opinion, the actors. Ignoring the neutrals for now, both the player and the opposing factions are composed out of the following distinct actors:
* The Sovereign
* Heroes
* Armies
* Cities
I'm not playing the current beta. But from what I can tell from other people's posts, enough is being done to make the sovereign, heroes, and armies fun to play with (even if the differences between the heroes and the sovereign have become rather vague).
As most of us probably know, beta 4 will address the city building mechanics. I'm really looking forward to this, because the current mechanics are the main reason I haven't played the current beta (besides having other stuff to do  ). They are quite boring imo, and don't in any way help to make the world feel alive. What they lack is character and a sense of agency (meaning that they don't seem to interact with the world). Since we've only had a few bits of information about what will be done in beta 4 (largely removing on-map building (yay!), and talk about a third resource), I'd like to share what I hope will be done.

Cities as regional capitals
I've always felt that there was something off about the scale of the world in Ewom and FE. There were only a couple of cities on a continent, and except for a few resources, a whole lot of nothing in between. I thought there should have been dozens of small towns and villages for each city, even if they wouldn't do much beyond produce a little tax and some food, but still capable of growing into a city if circumstances were right. But I realise now that would turn into a micromanagement nightmare, and would be more suited for a kingdom simulator rather than an empire building game. Having the cities act as a regional capital and simplifying the rural development around it is the way to go. Maybe that is how it's supposed to be in the game right now, but in that case the former need to be made clearer, and the latter is completely absent. I'll talk about rural development later, but lets start with cities.

Cities
Cities will need to feel more like cities that interact with their surroundings, while not diminishing the sense of vastness of the world (a big problem with the current sprawling cities). Limiting the city to one or only a few tiles will help. New tile design would be a big help too. So rather than having the hub be 3 houses, lets have a dozen or so small houses surrounding a central building. And to have more interaction with the surroundings, change the current fence/walls tiles by adding a bunch of crop fields outside the city (if appropriate for that environment, no fields of grain next to a desert city unless it is next to a river or oasis please). These are mainly just visual changes, but I think they would help a lot with how the game feels.

Districs
While I wasn't a fan of building everything in a city on the map, having a city expand a bit as it grows is not a bad idea. In some of his posts a while back, Brad suggested that you would be able to add a district to a city that would allow you to specialise that city. So you would place the district on the map, and that would unlock further buildings that you could build in that city. This idea is fine, but I think it could be expanded a little by either choosing a district to place on level up in stead of the buildings you can select now, or by being able to place them as an expensive building project. I'd go with one on level up, and limit districts to be placed only on one of the eight tiles surrounding the city hub.

So for example, when I found my first city, it's just one tile. There are some regular building available to build, like a workshop, barracks, palisade, etc. When the city reaches level 2, I choose a military district. This unlocks buildings like a garrison (less maintenance for stationed units), a training yard (reduces training time), a blacksmith (reduces metal costs), etc. At level 3 I choose a slum as a district. This doesn't unlock any new buildings, but it does increase the cities growth substantially, at the cost of some unrest. This is useful to either grow the city faster, or to keep it from shrinking while I keep training units in the city.

Special districts - Resources
I didn't like resources being absorbed into a city, but with the district system above it could work. If a resource is on one of the 8 tiles surrounding the hub, it can be incorporated into the city, and unlock some buildings. So a Mine would unlock a Deep Mine that is more productive but costs more maintenance, and a Death Shard could unlock a Sacrificial Temple, that increases the shards power at the cost of a number of citizens each turn.

Buildings
There need to be a lot more buildings that open up possibilities for the player, but be careful not to make the same mistake as with Ewom, where you needed to do research to unlock basic game features. So for instance, requiring a barracks to train troops is not a good idea, but requiring a barracks to train troops with a special trait could work.

There also need to be a lot less buildings that provide a generic +X% bonus to resource Y production. A few of these are ok as you should be able to specialise a city, but they should never be no-brainers. So either have their construction time be long enough that you have to balance it against building other projects, make it mutually exclusive with another useful building, or make its upkeep significant.

I'd definitely remove the +grain buildings, and replace them with something else:

Colonies
Since the name 'Outpost' is already being used and satellite sounds to spacey, I'll just call these structures colonies. These structures are the small villages that surround a city. What they do is provide (part of) the resource production of the tile they are build on to their controlling city. So a farming village would provide (half?) of the tile's food production, while a logging camp provides production points. This way you can have a city grow in a natural way, it will make the lands around the city more valuable, it will make them less boring, and (for better or worse) it will provide a nice soft target for raiders, slavers, and invading armies. They could be build either by placing one on city levelup, as a building project, or by pioneers (who should cost way more population, maybe 50?). The first (and second?) ring of tiles around a city hub should not be buildable, and tiles around a colony should not be buildable either (at the very least for a colony of the same type).

So, what do you all think? Any cool idea's for buildings, districts (with possible corresponding buildings), or colonies?