Combine half each of the olive oil, lemon juice, rosemary, salt, and pepper in a large bowl. Add the chicken thighs and toss to coat evenly. Set aside for 30 minutes to allow the chicken to absorb the flavors. 

In a separate medium bowl, combine the remaining olive oil, lemon juice, rosemary, salt, and pepper with the peaches, onions, and chiles and toss well. 

Heat the grill to medium. 

When the grill is hot, add the peach halves (flat side down), onion slices, and chile pieces. (Place the onions and chiles in a grill basket, if you have one, so they don't fall through the grates.) Grill the peaches, onions, and chiles until they are marked and slightly charred on one side, 2 to 3 minutes. Flip everything and grill for another 2 to 3 minutes. The peaches, onions, and chiles should retain some firmness; you do not want them to feel cooked all the way through. If you did not peel the peaches, the skin will curl up at the edges. Transfer to a serving platter, arranging everything so that the onions and chiles are scattered around the peach halves. 

Grill the chicken until a meat thermometer inserted in the thickest part of a thigh registers 165°F, 5 to 7 minutes on each side. Transfer to the serving platter, setting the cooked thighs right on top of the grilled peaches, onions, and chiles. Drizzle some of the spiced honey over the top and garnish with the mint before serving. Bring the remaining honey to the table in a small bowl so that your guests may serve themselves more if desired. 

Spiced Honey

Combine all the ingredients in a small saucepan, add 1/4 cup water, and bring to a simmer over medium heat. Once it simmers, give it a stir and remove from the heat. If not using right away, transfer to a storage container. Allow to cool completely before covering and storing at room temperature.