Yes, it should be possible. In the "rules.xml" file that you will find in the data folder (where you installed Rise of Nations) you will find an entry that looks like this:
"<CTW_WONDER_MIN_CIVICS value="4"/>"Changing the 4 to 2 or 3, like you want, shouldn't be hard at all. Just remember to back up the rules.xml file before making the change in case you need to go back to it.
Hope this helps.