|There has been work done using constraints on the beads in the following papers: J. Chem. Phys. 112, 8910 (2000) and J. Chem. Phys. 123, 154504 (2005) but the theory had not been derived as you suggested.|
Two recent papers have been published that justify the use of constraints on the beads to simulate quantum rigid bodies: J. Chem. Phys. 138, 184101 (2013) and J. Chem. Phys. 139, 184115 (2013).
The application of RATTLE/SHAKE correctly calculates the structural properties but requires a different energy estimator, but this can be calculated from the bead position and potential energy from the RPMD integrator.
I feel that this feature will be useful for many OpenMM users