For example, I think diplomatic options are rather poor in RoN. If you want your scenario's gameplay to be different, you can add more diplomatic options through scripting. So you can give the player the possibility to trade cities, for example(if the player presses the 2 key, let's say, a popup will appear that will ask the player if he accepts to give one of his cities for one of the nation 2's cities). Of course, this should depend on some conditions, like the number of buildings in the player's city should be equal with the number of buildings in the AI player's city etc.
EDIT: I've played your Archimedes scenario and it was great fun sometimes, but it eventually became too easy for my taste. I especially liked the first part of the scenario, in which the Romans were stronger and the game was more challenging. But after I wiped them out from my island everything became much easier, and the Romans weren't anymore much of a problem.
After that, I built the Colossus and and trained a large army, and I prepared to conquer them. But then I've noticed that the Romans' score was stagnant at roughly 9000, only growing from 8900 to 9030, then going down to 8900, and so on. Is that a bug? I'm asking this because I even let the game run attended for more than a half of an hour, and nothing changed, they didn't attacked me and their score remained the same. Then I crushed the Romans in the last 10 mins without any problem.
Overall, it was a great scenario, especially enjoyable in the beginning. I liked the fact the catapults were really useful, and thus Archimedes really played a significant part in this scenario. The only negative thing I have to say is about that possible bug. I also think it would've been better if the time limit had been 60, not 90 minutes.
[This message has been edited by LordBJ (edited 08-10-2010 @ 07:43 AM).]