Greetings ladies, gentlemen and developers. I know there are many of these (threads) but with a little luck this will still have some meaning.
1. Map resource diversification.
For example. For example the "Old Forest" provides materials. But since it's a forest perhaps it could also provide a small (like only 1 unit) amount of food from foraging and or hunting. Twilight bees provide food. However honey could be considered quite a luxury so maybe the Apiary could also provide a small prestige bonus as well, perhaps only if the city contains an inn. Likewise the honey of these "twilight" bees could have magical properties that enable mixing of various potions/consumables (something that could be considered for a later addition to the game). Basically mix it up a little when it comes to map resources.
In a similar fashion a fruit orchard could also provide a bit of prestige but only if you have a tavern by making cider and similar fruit based (alcoholic) beverages. Marble, aside from providing materials, is also a fairly luxurious type of stone used for the beautification of buildings which could also translate into a prestige bonus. Some of these luxurious resources like marble, honey, etc. could also provide additional gold if a trader is present in the city (this could perhaps be unlocked by research). The idea is to make the resources a bit more interesting and varied in their effects.
2. Spell diversification.
This has been mentioned a lot of times and I really feel it's important to have (attack) spells with effects a bit more interesting than just "deals up ti int. in damage". So hurling bolder can "stun" a unit for 1 turn. A lightning spell could "shock" the unit giving it a -1.0 action penalty for several turns. Kinetic blast (or whatever it's called) could push a unit away in a certain direction. Fire spells should have burning after effects. Etc., you get the point.
Also please make it more clear whether a unit is actually being affected by a spell. Whenever I cast the 'stab of ice' I am never quite sure whether the unit has been frozen or not. One should be able to click on a unit and get a small list in the bottom showing any effects the unit is currently under.
3. Equipment.
It's obvious that a lot of fixing/balancing is needed here but maybe I can suggest some less obvious things.
-Diversify the weapons a bit further. For example. Give the spear bonus attack if used by a mounted unit because it's a good charging weapon. Likewise give infantry units with spears a small attack bonus vs. mounted units, make them have a role. Give the dagger a speed/action bonus. Remove the hp bonus from the med. pack but allow it to slowly restore the hp of all units in the stack so we can have field medics/healers. Make the scout's pack a real scout's pack meaning movement + vision range bonus, not that senseless +1 defense. Messenger's pack seems kinda redundant now. Perhaps the mes. pack should be a requirement for initiating diplomatic contact. That's what I though it was when I first saw it. In such a case it should give a movement bonus and it could have great synergy with horses/wargs so you can have mounted messengers. That's basically how "medieval" kingdoms communicated.
-Diversify the equipment into spellcasting and warrior items. Instead of all characters going for heavy armour provide equipment for robed/cloth spell caster types so we can specialize and build the type of character we want.
-Allow for "pet" equipment. For example a pet wolf that provides +1 vision range (good sniffer/tracker) and +1 attack as it fights with you. It would appear beside the unit on the battle map as part of the "squad". Trained falcon +2 vision range. Pet/familiar owl, +2 essence or +1 intelligence. Etc.
-Diversify the mounts. A charge ability for horses that provides bonus attack provided the unit has traveled at least one empty square before striking. Alternatively allow "charging" to occur only on the 1st strike regardless of distance traveled. Give wargs a howl ability that lowers the attack of surrounding enemies by scaring them or something like that.
- Allow units to wear some clothes under the armour so their skin doesn't show between the "cracks", mostly in the knee area. It looks quite silly. Or at least make the armour pieces "join" better.
Armour is not worn over a naked body anyway.
Provide some pants/skirts for women as they have nothing to wear below the belt with their shirt items.
-More weapons like javelins for example. Low range but better attack than arrows. Low def. bucklers that can be worn on the lower arm and used with 2-handed weapons.
4. Battle Map.
More different tactical tiles. Forest tiles should provide superior defense vs. ranged weapons. High ground that provides range/attack bonuses for bows. Swamps and other difficult terrain that costs move action points to traverse. Exposed, open areas that make units vulnerable to ranged weapons. Etc.
Formations for unit battalions. Raised shields for bonus def. vs. arrows. Shield wall for bonus def vs. melee. Wedge for bonus attack, especially when mounted. Etc. Formations unlocked via research. Changing formations should cost action points.
5. More interesting hero development. Allow heroes/adventurers to gain "perks" (every few levels) in addition to their stat points. Let those perks have levels. So for example, "novice trader" +1 gildar, "journeyman trader" +2 gildar, "master trader" +3 gildar.
Further examples, scout +1 movement/+1 vision, tracker +2 move/vision, explorer +3move/vision.
Tactitian +1 att/def for all units in stack, commander +2 att/def, general +3 att/def.
Charismatic 10% cheaper heroes, +X morale bonus in battle. Inspirational 20% cheaper heroes +Y morale. Great Leader, 25% cheaper heros +Z morale.
There's all kinds of stuff one can think off. Make heroes more interesting and allow us to develop "administrative" heroes who give income/production/research bonuses and "general/warrior" heroes who lead men into battle.
That's it for now, thanks for reading. 
