I have thoroughly enjoyed playing Succession Games. If it weren't for the SG community here (and the PBEM community at CDZ) I would have stopped playing the game a long time ago. But sadly I am of the opinion that C3C is broken. The main reasons for that are:
-The AI doesn't attack units that are far superior to their strongest attack unit. This means that a healthy army with 4 pikes is safe until bombers and tanks. It also means that an elite infantry is safe vs a vet cavalry unit. So the strongest defense in the early industrial age is safe from the strongest offense until tanks. Simply unacceptable

The consequence of this is that the game is far easier than PTW. I congratulate everyone beating AWD, AWS or other Sid variants in C3C - it is certainly an achievement-, but to me this all is less of an achievement than beating AWD in PTW and vanilla. EDIT (Looking for a better explanation): The game can change from ultra difficult to ultra easy once you get your first military leader and turn it into a spear/pike/knight army. Getting your first army up and running is too important imvho.
-The AI hardly ever builds armies. I haven't seen ONE AI army in all my C3C games. Others have reported that they did see them (like LKendter), but this only shows that they DO exist and how rare they are.
These two issues are not to be underestimated. You can basically invade the AI without being counter-attacked. Perfect example is MM1 - Sid defiant. We have to face huge amounts of rifles, cavalry and guerillas (vs America), but they all refuse to attack elite infantries and healthy berzerk armies.
There are other flaws as well, but these are far less important to me. I would happily start up new SG's without them being solved:
-SGL's can't trigger a REAL Scientific Golden Age. This new concept of C3C has never worked.
-The infamous submarine bug has never 'bugged' me (I never noticed the bug, my games mostly didn't last this long).
-AI can't handle the seafaring trait. The concept of suicide galley got a new meaning with this trait, but the AI will not use it.
-The AI can't understand that non-combat units can be captured by non-amphibious units from boats. You can still block the coast-line with workers unless you are playing a human opponent.
I have tried playing games with all kinds of restrictions, but this simply doesn't do it for me.