Prepare Smoky French Dressing: In a blender, combine the ketchup with the mayonnaise, vinegar, mustard, garlic and chipotle. Puree until smooth. Season with salt.
Note: The smoky French dressing can be made in advance and refrigerated for up to 3 days.
In a large pot of boiling salted water, cook the asparagus until bright green, about 2 minutes. Drain the asparagus and spread them out on a large baking sheet to cool.
Preheat a large grill pan. Drizzle the asparagus with olive oil and season with salt. Grill over moderately high heat, turning, until tender and lightly charred, about 3 minutes.
Spread the cut sides of each roll with 3 tablespoons of the smoky French dressing. Arrange the grilled asparagus on the subs and top with the raisins, scallions and crumbled feta. Close the sandwiches and serve.