What about the following changes to the Dovollio.
Leaders:
Charadon gains charismatic, making him aggressive, charismatic, and barbarian.
Mahala gains expansive, making her raiders, expansive, and ingeneous
Lucian:
Change him to a Dovollio Great General that the Dovollio start with. Then give the Dovollio civ-specific great generals. These great generals would be unable to build command posts or recruit, but would instead give different bonus's when attached to units. Specifically, they would grant the current +1 strength, +1xp from combat, as they do right now. But they would also double the units metal bonus. This would mean that he would grant +1 strength to a unit without metal, +3 to a unit with bronze, +5 to a unit with Iron, and +9 to a unit with mithril (note, this is including the weapon promotions with it). This would give them a bonus core of units who are stronger than others, but to get them they would have to give up specialists. Then, give them a civ-specific command post that doesn't require organized, and gives +1 GC points. That and the wonders which grant GC points would be the only ways for them to get these great commanders, which would keep it in check.
Flavor:
Flavorwise, they are supposed to love the tundra. Currently, tundra is as worthless to them as to anyone else, and there is no way to get tundra. So, give them +1 hammer, +1 commerce from tundra, +1 food from ice, and give their adepts a spell that can turn plains to tundra (optionally, make this only work within their own borders). Combined with sun to scorch ice to tundra, and grassland to plains, and water to turn deserts to plains, they can become a tundra dwelling civ that can terraform their own territory.
Secondly, give them a unique improvement that can only be built on tundra, and cannot be built next to another version of the same improvement (must be 1 tile between them, instead of two like pirate coves), and have this improvement give +2 food, a few commerce, a chance to discover hunting resources, and the ability to be built under forests (plus a bonus for hunting resources found in it).
Third flavor point. Upgrading units is a prime tenant of the dovollio philosophy. So how about giving their melee units a chance to upgrade (if the requisite tech is available) to a higher level unit on combat victory or level up. Units can still be upgraded normally, but they can also be upgraded in this manner. If you want slightly more flavor, have beastmen be able to upgrade to Sons of Asena in this manner at mining, and Sons of Asena to Battlemasters at smelting.
Worldspell:
Right now, their worldspell allows them to get a bunch of wolves - semi-useful in the early game, worthless aside from rushing and getting wolf-pens in cities. So an idea to make it more useful, and allow them their rushing flavor, and allow more strength in the midgame. Change the worldspell to unlock at bronze working or smelting. Then, have it reduce the population of all cities to 1. For every population removed, give 1-3 beastmen with the free-unit promotion (1% chance to wear off each turn). Increase the number given by 1 each for running military state and conquest. Note, I said beastmen, so to upgrade them to axmen would still require plenty of gold.
Hero:
The war machine is a neat toy. I doubt that anyone who has actually played the dovollio have ever actually used it though. With their flavor though, their hero HAS to be a combat unit - no dovollio would follow some weakling mage or priest. On this note, it would seem wise for the leader of this civ to lead it where it belongs - on the battlefield.
Therefore, Playing as Charadon would give you the hero Charadon. Charadon would replace Lucian, available at the start of the game. Then, at bronze working he would be able to take the hero promotion. In addition, he would be able to upgrade along the melee line.
Mahala would take the field at warfare. She would give you a great general (named Mahala of course), who can attach to any unit, just like Lucian. But, in addition to the great general effects, she would also give the unit she attaches to the Hero promotion.
Hmm... I might see about making this into a little modmod myself. It would certaintly make me interested in playing them.
-Colin