This is my story of Epic 39 from Realms Beyond Civilization. The scenario setup is there, and repeated here.
Scenario concept: To try out the new and improved Specialists in Conquests.
VARIANT RULE: Any tile that can be irrigated may not be mined or have a forest planted on it. This would apply to grassland, plains, and desert. Hills, mountains, and tundra are free to be mined, and tundra can be forested. If you acquire rival territory that has such mined tiles, your cities cannot use them until you convert the existing improvements to irrigation.
VARIANT RULE: You may not switch to Republic or Democracy.
Scoring: Ranked by fastest finish in each victory type.
Strategy: Large quantities of food will greatly encourage the use of specialist citizens, and lack of the Republic/ Democracy trade boost will make the specialists relatively more valuable economically. These rules may also make the new and improved population-rushing governments more attractive, and the Celts are religious for a late-game government swap -- or you can stick with good old Monarchy.
The Celts aren't truly a new civ, but did get some significant changes in the expansion. Managing the specialists will require city micromanagement, but it should be tolerable on a small map. Finally, remember that you may not plant new forests (except for tundra), so you may want to conserve native forests for shield production.