This is one of the most balanced and fun colloseum editions available, with 4 early levels before the standard ones, and a final game-ender level for anyone with over 2000 kills (those bits I didn't add, they were in the advanced base version I used).
What I did:
~Ensured it is always balanced no matter your civ or starting age, YOU CAN USE THIS IN POST-IMPERIAL!
~Bloodfactories give everyone a musketeer every minute, and a target for early gameplay armies not yet ready to assault the walls.
~No cheap stuff like making boats; harbours are disabled
~Is completely balanced for all players, player 1 has no advantages over the others (unlike some colloseum's I've played lol)
~ Play it once and you will fall in love with it.
HG forces me to submit it as a .zip file instead of a .age3scny file, so just use 7Zip or something to extract and place it in your scenarios folder (usually C:\Users\USERNAME\Documents\My Games\Age of Empires 3\Scenario for windows 7 computers).