If you are a nominalist, then it makes perfect sense to speak of Christ alone, Scripture alone, grace alone and faith alone, because for nominalists, the state of singularity, of independence is what is real. For them, it is a metaphysical "compliment" to view a thing in its autonomy, in its aloneness.
If you are an extreme realist (Platonist) then it makes absolutely no sense to speak of a thing apart from its Ideal; and ultimately, it makes no sense to speak of individual Forms apart from the Good; or to speak of the Good apart from its necessary "overflowing" into the rest of the universe. Everything either is a form or an instantiation of that form.
If you are a moderate realist like Aristotle, then it is possible to speak of particular substances, but they are not absolutely independent of one another, because they are all universal forms individuated by prime matter. If you are a moderate realist like Thomas Aquinas, it is impossible to speak of any creature apart from God, the Creator and Sustainer; for not only does it relate to Him in terms of its beginning, but its existence must also be continuously conserved by Him.
Thus realists are unable to speak of anything absolutely alone. Christian realists hold that God is three persons in one substance: relational to the core. For them, it is a metaphysical insult--nay, perhaps even heresy-- to speak only of autonomy, and ignore the fundamental relational character of reality.
Hence realists do not speak of Christ alone, but Christ and His Church. They do not understand sola scriptura, but they do understand scripture and tradition. They do not preach sola gratia, but rather grace and cooperation. They do not teach sola fides; instead, they teach faith and works.
Does your theology depend on your metaphysics? Or does your metaphysics depend on your theology? Maybe its a both/and! ; )