Boozy Fruit Crumble - Testing

I've adpted the Berry Crumble to include the boozy fruit that's leftover from when I make liqueurs. Not bad, I must say. The apple worked really well to soften the alcoholic edge of the boozy fruit, but I felt like it was a bit dry. It could be the King apple varietal I used that isn't very juicy after languishing in the refrigerator all winter. I'm curious about a couple of things - what if I mixed in half fresh/frozen blackberries, substituting half the apple for it? Also, or maybe instead, what about adding a couple of tablespoons of the actual liqueur to the fruit layer?

½ cup (1.8oz/50g) walnuts or hazelnuts, toasted and finely chopped

Crumble Filling

¾ cup (6oz/170g) boozy plums, pitted and sliced

¾ cup (6oz/170g) boozy blackberries

1½ cups (12oz/340g) apples, peeled, cored and sliced

OR 1/2 the apple and the other half fresh blackberries?

5 Tbsps. (35g) flour

1 Tbsps. lemon juice

Crumble Topping

1½ cups (180g) flour

½ cup (110g) brown sugar

2 Tbsps. (25g) granulated sugar

½ tsp. Poudre Douce

½ tsp. salt 

½ cup + 1 tbsp (4.6oz/130g) butter, melted

1. Preheat oven to 350°F. Grease a 9" glass baking dish and set aside.
2. While the oven is preheating, put the nuts on a baking sheet to toast, about 15 minutes.

Prepare the Filling 

1. Combine the plums, blackberries and apples with the flour and lemon juice in a medium bowl and stir to combine. Allow to sit for 15 minutes, stirring occasionally.
2. Spread evenly into the bottom of the prepared dish.

Prepare the Crumble Topping

1. Melt the butter.
2. In a medium bowl put the flour, brown sugar, granulated sugar, cinnamon, salt and nuts and give it a quick stir.
3. Add the butter and mix together until completely combined.
4. Sprinkle the crumble topping on top of the fruit mixture in the prepared dish spreading it evenly.
5. Bake for 40 to 50 minutes until bubbly and golden. 
6. Let cool for at least 15 minutes to allow the filling to thicken.