Since Roman soldiers were famed for their engineering skills, it makes sense for their list of army constructions to be the most expansive. I've listed these from most feasible to least feasible:
1.
Watchtower: Using Davide Cool's model. Already under way, I think, so I will not concern myself any further with it.
2.
Small (i.e. vanilla) fort: I would like this to be as vanilla, except I am intrigued by the possiblity of limiting its garrison. I may be mixing this ability with Kingdoms modelling, but would it be at all possible to limit the small fort's garrison to about 5 units? It should be part of the appeal of the larger forts that they can house more men.
3.
Medium fort: Just what it says on the tin. A semi-permanent, wooden fortification, of substantially larger proportions than it's smaller brother, possibly with wooden huts as opposed to tents. If possible, I would up the unit limit to 10.
4.
Large Fort: A permanent, Roman campus, with stone fortifications, mock-stone wooden buildings and the now-trademark Roman Fort Plan streets. This would need to be of, not epic, but sizeable proportions, and suffice it to say it would need to be expensive to build and run. It could also have buildings in the periphery, representing the accomodation of the camp hangers-on.
-------------------------Watershed: Now is where I get ambitious-------------------------
5.
Upgrade Roads: Consider the dilemma. Legio XXV has been marching into the Numidian desert for many months, trying to rendezvous with Legio IX. The FOW prevents easy vision, and the difficult conditions mean that the Legion is making barely any progress. Thus, it would be brilliant to have a feature whereby, in enemy territory, a legion could camp down for a turn or so and simply upgrade the roads. Suffice it to say that this would mean no roads -> dirt roads. If there are existing dirt roads, it makes little sense to upgrade these to cobbled roads! It many not be an oft-used feature, but it must be possible to implement, and if the AI was not allowed to use it for all and sundryit could be of interest to the player. Obviously it would be far more expensive to use the legions to make the roads than it would be to build them yourself, hence keeping the feature for enemy territory.
6.
Continuous wall construction: Now, I'm sure we are all aware of how the latter-day Roman Empire relied heavily on such fortifications to keep Germania out, and to a lesser extent Scots. Also, I am fairly sure that Viking Invasion II have done just such a thing, and built continuous walls. Now, Cherryfunk, I seem to recall that you work for VI2. Might it be possible for us to very nicely ask them if we could borrow their walls, or at least be told how to do them?
-------------------------Watershed: Now is where I get mad-------------------------
7.
Bridge Construction/Demolition: Not sure if this is at all possible, but wouldn't it be cool to retreat, puling down the bridge in your wake? And then have your enemy faced with a strategic decision: Does he rebuild it and waste time or does he try and find another route? I just think this is too cool an idea to let slip up, so I thought I'd ask.
---THE BARBARIANS---
1.
Usual suspects, watchtower, small fort, whatever.
2.
Hill Fort: Tone had the idea for this. If anyone here has ever been to or seen Maiden Castle, they will know what I am talking about. Several peaks and troughs of unmitigated awesomeness. I already have lots of images in my mind of Romans being cut down by arrows as they ascend out of one of the countless ditches. (It will also make an awesome challenge if you are playing the Romans, as I will be!

I anticipate that this fort will also need a "footprint" of land to be slapped onto the campaign map, you know, what with al the hills and ditches and whatnot.
I can think of nothing for Greeks and Carthaginians, but if anyone here (ahem, Keravnos, swhunter) has any suggestions, I can add them to the list.
Sooooo, what do we think? Are at least some of these ideas feasible? I can handle the modelling, but there is a fair bit of coding to be done too. Anyone enthusiastic?
I feel I should also say that this lot of things may actually take longer to do than the 2.0 release, but I daresay it could all be patched in at a later date, assuming the dev team doesn't just disband after 2.0's release!
Thanks for your time,
RHG.