Can agnosticism every be on the side of faith? Can a non-believer ever be a saint?
from the lecture Miguel de Unamuno, Saint Emmanuel the Good, Martyr
You ask: Can a non-believer be a saint?
I am assuming that when you refer to a "saint," you mean a saint as defined and declared by the Roman Catholic Church. I am far from being an expert on Roman Catholic doctrine (if you look at my profile picture, you might see why!) but I did find on the web a note from the Vatican that outlines the procedures for being declared a saint (see link below).
One of the first qualifications for sainthood is that the person has to have been "heroic" in the "theological virtues: faith, hope and charity."
I would assume that an openly agnostic person would not be considered "heroic" in the virtue of faith, and would therefore not be eligible for sainthood.
(Some other qualifications for sainthood: the person must be "heroic" in the "cardinal virtues" of "prudence, justice, temperance and fortitude"; the person must perform two miracles.)
If you think of agnosticism as someone who isn't sure, then, yes, an agnostic could be on the side of faith. Some agnostics want to believe, and may wish they could believe, but can't rationally bring themselves to do so.
Later Victorians and early moderns are known for having faced a crisis in faith such as this. With the growth of scientific thought, Darwin's new ideas, the failure of the industrial revolution to bring about a society better for all, etc., some found it no longer possible to believe as firmly as they once had. That doesn't mean they didn't want to.
Matthew Arnold's poem, "Dover Beach," is a famous example of someone who wants to believe like he once did, but is no longer able to do so:
The sea of Faith
Was once, too, at the full, and round earth's shore
Lay like the folds of a bright girdle furled.
But now I only hear
Its melancholy, long, withdrawing roar,
Retreating, to the breath
Of the night wind, down the vast edges drear
And naked shingles of the world.