Some tips:
1) Try Jirisys' mega mod. It is for Alexander, if you have it. Makes A.I. somehat smarter.
2) Play VH/H.
3) In Jirisys' mega mod, there is a realistic movement mod. But you can edit the movement points yourself. Making them a little more than double (or just double) as they are now, will help A.I. expand more, cos' the strong rebels inside rebel cities will start to leave cities undefended (you'll see a big difference). I think the file you 'll have to modify is the "descr_strat". It has a line at the start saying "movement points". It is 60, make it 120 or 140.
4) Romans and Carthage are "easy" factions. All the others are more challenging. And some are much more.
5) Playing with a different faction cannot give you the same feeling as playing as Romans, cos' there is a big diversity between all factions. Keeping an eye (or both

) on traits does add to the different feeling very much.