Hey, i posted some of these ideas in other forums.  However, Id like to post here as well to see what people thought.  These would be relatively easy to implement (i think).  All in all, I love how the game is shaping up post 3B.  I honestly dont see myself buying any other games for awhile. Im not putting too much about tactical battles as there is already an active thread on that.

I like the current 'imbue' system, as well as the 'essence potions' that you can use to create mages.  It makes mages rare, and with combat spells like Ice Bolt one-shotting heroes/units, sufficiently powerful. some ideas though to make it better:

A) Wizards Tower: (ripped from MOM, AoW)  High level improvement (city level 4 or 5?). Can build one per civ.  This tower would allow the soverign to cast in ALL battles in his/her terriotry, and cast enchants in ALL areas of territory.  These enchants/battles would have increasing cost away from the tower.

This would a) give sovereigns a reason to 'Rule' from a tower end game, and give the feeling of an 'epic, powerful caster'.  Prehaps in such a tower, the sovereign could also cast (for a mana penelty) in non-home territory battles were they have a 'hero' for a penalty? It would be fun becasue a) itll greatly improve the sovereigns power, make more use of heroes in important late game battles and c) force a decision between a sovereign leaving their territory to invade (for maximum spell pawnage), or stay at home to continue defending the realm.

'Tactics' Skill/Great General: Ripped from HoMM 5)

This idea is a skill for heroes/sovereigns to have an 'ability' for leading troups/tactical ability.  This would be a check against an opposing army: if higher 'tactic' ability, can see enemy troop placement prior to tactical battle and then place troops accordingly.  A high level general over none (or a low level) would be so superior that before the battle starts, they could place cavalry at an enemies flank, ambush (with soldier's surrounding the enemy at start), etc.

Why it would be fun: make a 'general' warrior hero as opposed to simple 'champion' warrior hero, giving more variability and use to non-mage heroes in combat.

C) Conquered Populations:

If a city is conquered, keep the same race their with associated abilities.  IE if I'm controlling the Gilden, and I conquer a Trog City (with their superior troops), I want to be able to train superior Trog heavy infantry.  

Migration: ala AOW.  If I conquer that Trog city, and its not as good as my Capitar humans at economy, I'd like an option to migrate them out.  Move them ala Andrew Jackson's great migration.

D) Unit Design:

I want to ride dragons. Please?If i get a dragon, please give an option for my casting hero/general hero to ride it. 

Stealth units would be cool as well (rangers/scouts/thieves in enemy territory)

Archers currently feel overpowered and only one bow availible.  I assume this is going to be worked out.

E) Heirs/Dynasty: LOTS OF POTENTIAL. 3B a lot less kids....made the game a little less fun.

Ive posted a lot about that in the past. don't want to rehash too much- but ability to train/interact with heirs as they are growing up would be cool.  Heirs starting out more powerful would be cool as well (so far theyre pretty weak).

Random heir events (such as running off and getting married to a peasant as opposed to the arranged marriage you set up) would be awesome.

F) Essence/Shards:

I like that you have to imbue to get casters.  Please keep.  I'd like the ability to imbue rings/weaponry.  Sounds like thats coming with weapon forging.

Shards: I'm unclear of their current function.  Increasing Sovereign essence (as proposed earlier) would be awesome, and make them valuable.  Making them required for HIGH level spells of certain 'colors' would be nice (a guy with a fire book can always cast firebolt and fireball.  But if he wants to call flaming meteors of uber pwnage, he needs a fire shard).

Why it would be fun:  right now, shards dont seem valuable ( i wont fight for them, but I will for horses/iron deposits).  Lore wise theyre uber powerful, and I like this.  It would be nice to have these changes (but make sure those spellbooks are still useful without having the requisite shard type).