Can spin polarisation restrict the possible types of LHC proton-proton collisions? Despite the massive luminosity at the LHC, it's probably correct to say that no two collisions are ever identical, even up to symmetry. Not only are there all possible impact parameters, but the individual protons contain 3 quarks each and so the collision details depend on the state of the internal wavefunctions too.
My question is whether a spin polarisation imposed upon a proton in some way aligns the quark wavefunctions to the spin direction?
Were this to be the case, would this not serve as a valuable collision filter?
 A: You are requesting polarized beams, which are much harder to prepare than unpolarized ones. The decisions for the LHC were to reach maximum luminosity so as to have a higher probability of discovering new resonances and effects.
The RHIC accelerator provides polarized proton beams:

December 17, 2001
UPTON, NY — The newest and largest particle accelerator at the U.S. Department of Energy's Brookhaven National Laboratory is taking a break from recreating the conditions of the early universe to investigate another fundamental question that has puzzled physicists: Where do protons get their spin, a property of elementary particles as basic as mass and electrical charge? To begin to answer the question, the Relativistic Heavy Ion Collider (RHIC) has accelerated beams of polarized protons to the highest energy ever, and will begin colliding the beams this week.
"These will be the first-ever experiments where the protons in two colliding beams are all spinning in a controlled direction," said Thomas Roser, head of the Brookhaven accelerator group running the project.

Interesting results have come out  but no model changing discoveries as to the structure of a proton so far  , the publication is of 2013.

My question is whether a spin polarisation imposed upon a proton in some way aligns the quark wavefunctions to the spin direction?

The quark wavefunctions will be correlated to the spin state of the proton, in a polarized beams experiment, and certainly more information would be available for checking models.

Were this to be the case, would this not serve as a valuable collision filter?

Sure for detailed studies of modeling the strong interaction and the behavior of the constituent quarks and the quark gluon sea. The experiments at RHIC are studying polarized data to investigate the spin of the constituents of the proton.
