I think it's the tremendous saltiness that results in most recipes telling you to get rid of the insides. The skin just doesn't pick up salt the way the insides do. However, it does seem a shame to waste all that good juice. I'll be interested to learn other ways you find to use your preserved lemons (which look lovely, by the way).
Preserved lemons are used in a number of classic Moroccan tagines, though it appears in other Moroccan dishes. One of my favorite uses is in this Moroccan salad (but definitely get rid of the insides of the lemon for this.
Shalada bil Matesha Basila w’l’Hamad m’Rakad
(Tomato, Onion, and Preserved Lemon Salad)
2 lb. firm, ripe tomatoes (plum tomatoes work well)
1 small red onion
1/2 preserved lemon
5 Tbs. olive oil
1 Tbs. lemon juice
1 clove garlic, crushed
3 Tbs. finely chopped fresh parsley
3 Tbs. finely chopped fresh cilantro
1/4 tsp. ground cumin
1/4 tsp. paprika
salt and freshly ground black pepper (to taste)
Cut the tomatoes into small cubes. Cut the onion in half, then slice the halves as thinly as possible and separate into half rings. Place the tomatoes and onion in a bowl.
Discard the pulp of the preserved lemon and rinse the peel well. Dry with paper towels, then cut into fine strips. Add to the tomatoes and onion rings. Add the chopped parsley and cilantro over the salad, and toss lightly.
Beat the olive oil, lemon juice, garlic, spices, salt and pepper in a small bowl or measuring cup. Pour over the salad, toss lightly to cover, and let stand for 30 minutes before serving.