  We investigate structural properties of massive galaxy populations in the
central regions of five very massive galaxy clusters at z~1.4-1.7 from the
South Pole Telescope Sunyaev Zel'dovich effect survey. We probe the connection
between galaxy structure and broad stellar population properties, at stellar
masses log(M/Msun)>10.85. We find that quiescent and star-forming cluster
galaxy populations are largely dominated by bulge- and disk-dominated sources,
respectively, with relative contributions consistent with those of field
counterparts. At the same time, the enhanced quiescent galaxy fraction observed
in these clusters with respect to the coeval field is reflected in a
significant morphology-density relation, with bulge-dominated galaxies clearly
dominating the massive galaxy population in these clusters already at z~1.5. At
face value, these observations show no significant environmental signatures in
the correlation between broad structural and stellar population properties. In
particular, the Sersic index and axis ratio distribution of massive, quiescent
sources are consistent with field counterparts, in spite of the enhanced
quiescent galaxy fraction in clusters. This consistency suggests a tight
connection between quenching and structural evolution towards a bulge-dominated
morphology, at least in the probed cluster regions and galaxy stellar mass
range, irrespective of environment-related processes affecting star formation
in cluster galaxies. We also probe the stellar mass vs. size relation of
cluster galaxies, and find that star-forming and quiescent sources populate the
mass-size plane in a manner largely similar to their field counterparts, with
no evidence of a significant size difference for any probed sub-population. In
particular, both quiescent and bulge-dominated cluster galaxies have average
sizes at fixed stellar mass consistent with their counterparts in the field.
