I put this already in the poll thread:
Rome
- Add more provinces, more countries, more tribes. One of the problems of Rome is that the map is too small, the countries too few and the big ones too dominating. If it is set in the Alexander time, Greece should be an interesting place, not a 5 province thing. Make it much more complete, add small countries, city states. Do this for all the map because the current map is too simple. Provinces are so big that Carthage touches the Lusitanians easily and then obviously steamroll them. The big 5 are too dominating and few provinces only helps them in steamrolling small, 1-2 province countries.
- Of course, expanded map. The obvious step in an Alexander based expansion is to expand it wast to the Indus and north to the Aral sea at max. Also adding Meroe. This is the minimum. However, when I imagine a start at a date the macedonian height, a map like this would be hilarious. You would own half the map and then proceed to steamroll smallish Rome and Carthage. I mod Rome too and again, referring my mod this time for Rome (sorry for the publicity, but it really completes what goes in my mind), Magna Terra, I wanted to make it possible to start at an Alexandrian time and have fun. How? Including all the known world. Ouch! India, the giant steppes of Central Asia, Arabia, Nubia and Ethiopia, China. Too much? Surely for an expansion, but I think it would be a much more fun game with an Alexandrian empire with much more to conquer. And suddenly the game is not the monotonous big 5 in Europe, we can start at a post-Maurya India and with the warring states in China. The Seleucid syndrome (east backs safe) would be solved too by India added (this syndrome would also probably exist in a Macedonia that ends in the Indus). If well done, it increases the fun, as it will be very different experiences. We can pick a giant empire and go for world conquest. Of course these big empires require what I'll refer in the next point.
- Make it enough funny to play with our country and characters BY ITSELF. That is, in big empires like Rome and Macedonia, give us toys to make us entertained and thrilled and think to conquer our neighbours later or make us suffer the consequences of a major war with an weakened ruler internal network. Make families matter, make governors/government interaction much more visible, make us keep an eye in what's going on in our empire. Create governors/governors interaction. Family rivalries/alliances. Political character marriages. Use our armies not to conquer other countries but to remove governors in mini-civil-wars. Allow us to use military stacks of doom for conquest only after we have our empire internally stable (example: make sure governor A of a important province will not use its own military strength to create a civil war by ensuring it is allied with our family and giving it prestige and all he wants, while having national armies close to governor B that likes to rebel), making conquests slower and helping the small countries to have a chance to breathe with their smaller manpower. This "country only game" would pave the way to a further expansion dealing with the Roman Empire.
- Make us care about characters, not only by their skill but also by their political/wealth importance. Guy A sucks, but he is powerful, so we must do something to make him entertained otherwise our ruler/dynasty may be start to be looked as weaker compared to theirs, affecting income, loyalty, etc. Create more positions for characters than just tech guy/governor/government. Link families and/or character to regions and/or create a regional influence ranking by family, adding lots of possible events and help us sort all the characters of our empire. Example: family X is very influent in Galatia. Maybe it's better to allow them to dominate the local businesses (micromanageable or automatic - like a turn on/off switch then for all the jobs in that region for that family)
- More decisions and laws. Missions are too blank too. Give us a big reward for unifying Greece.
- More diplomatic interaction between countries. Nothing happens in EU Rome diplomatically. Barbarian/Civilized country/provinces interactions - take this money, don't attack us. Grand alliances of small countries, defensive alliances.
- Tribe migrations (can be left for an hypothetical Roman Empire expansion), internal administration too but made different for tribes.