I like what I have seen of the scenario creation tools for beta 5, but there are a few additional feature I would love to see.
1)Setting starting gold, capital production and starting armies for each side. E.g. I want to turn one side into a dwarf clan, I can do this by giving them a stack of dwarves, and setting up dwarf production at the capitol.
2)Multiple starting cities (only one capitol) and armies. E.g. I want to make one side an empire in decline, so I set them up with several cities spread across the map, garrisoned by weak units. I want another side to be an orcish horde, so I give them some stacks of orcs scattered around the map.
3)DLR-style, side-specific unit restrictions. E.g. I want the black side to be evil incarnate, so I restrict them from building pegasi, crusaders , archons and elves.
4)Side specific triggers. E.g. If the green side (the Sylvan Lord) controls 3 specific cities he gets some elves as a reward. No other side may receive this reward.
5)Triggers that send messages to the triggering player (to keep them informed of what they should be doing, or explain what just happened).