This is probably a bad idea but I'll toss it out here. I was thinking about the disadvantages of a jungle start. You have to wait for iron working to get to some of your resources. Why is that anyway? Can you cut through an oak with a bronze axe but not jungle plants and trees. You probably would just burn it down. That's how they clear jungles today, regrettable as it is. So in game how would this work? You could have a match icon for your worker. You could choose to set fire to the forest or jungle to clear it. You'd get no production boost for doing this like if you waited for the prerequisite techs for chopping. There'd also be a small chance that the fire would spread to an adjacent tile. The fire would be visible, like fallout, and damage units over time. You could even add a temporary growth penalty to nearby cities from the smoke. I can just imagine my scout making it to Monty's territory and seeing an out of control forest fire around his cities. Or maybe you deliberately set a forest fire in front of an invading force. Make it so you can only set a fire in your controlled territory to prevent setting your neighbors forests on fire. And you'd need an extinguish fire icon for workers so you could put it out if it spreads too much.