My Suggestions.

[Bishop]

Firstly I have every confidence the finished product will be fantastic and these ideas may have already been thought of or suggested. That said here are some idea's I hope you will find fun.

Nomadic Tribes:
I would love to see and play as a more nomadic tribe travelling in a caravan and setting up camp in a region to trade with the locals or simply plunder, pillage and pilfer before packing up and moving on. As a player perhaps you could take it to a massive scale (much like the Mongol Empire).

Formations:
If I may quote Wikipedia "A sheltron (also sceld-trome, schiltrom or shiltron) is a compact body of troops forming a battle array, shield wall or phalanx." I think this could be a fun and interesting addition and even the odds a bit when you find your squad outnumbered.

Society & Culture:
What ethos you and your people have. Democracy, Militarism, Monarchy, Tribal, Theocracy, Dictatorship, Republic? These could apply different boons and drawbacks to a faction and even affect pre-battle preparations (would they check their gear, pray or even dance?).

Information & Alerts:
A small text window giving the player useful information would be nice say for example if one of your men spot or engage a hostile or when a building/research is complete (useful for when you are pre-occupied with something else).

Watchtowers:
Allows a squad member to act as a lookout for a small settlement before walls are erected or possibly as part of the wall itself. These would also act as excellent platforms for bowmen to pick off enemies.

I would love watchtowers.