4vs4 can be decent. For example classic europe cities works very well, rise of rome is very good for 4vs4, but for larger games there are hardly any big enough maps to work with. IMO 0% luck is definitely required, with only 2-3 gift cards on the start and possibly a single airlift (or no airlift). One of the main problems in big team games is the lack of influence of every player on the whole board. I'd definitely avoid Sengoku or other more "lenghtened" maps and try my best with full or cities distribution. Rise of Rome might be a good start to find strategic settings for 5vs5 (maybe work your way up from there). For example:
- Rise of rome full distribution 5vs5
- 3 starts of 4 per player
- 2 gift cards
- 0% luck straight round
- 4 base income
That's just of the top of my head, map topography might be good enough to handle such a game. Of coure one of the other problems is in order to try it out real-time you'll need `0 decent players, and I know it's not that easy to find people for 3vs3.
That setting might be good enough, because the map is fluid enough despite being big. Also with 3 starts you will have to spread out.
I am not entirely convinced because of single 1-bonuses, so you might even consider lowering base income to 3.