  Whether or not femto-scale droplets of quark-gluon plasma (QGP) are formed in
so-called small systems at high-energy colliders is a pressing question in the
phenomenology of the strong interaction. For proton-proton or proton-nucleus
collisions the answer is inconclusive due to the large theoretical
uncertainties plaguing the description of these processes. While upcoming data
on collisions of $^{16}$O nuclei may mitigate these uncertainties in the near
future, here we demonstrate the unique possibilities offered by complementing
$^{16}$O$^{16}$O data with collisions of $^{20}$Ne ions. We couple both NLEFT
and PGCM ab initio descriptions of the structure of $^{20}$Ne and $^{16}$O to
hydrodynamic simulations of $^{16}$O$^{16}$O and $^{20}$Ne$^{20}$Ne collisions
at high energy. We isolate the imprints of the bowling-pin shape of $^{20}$Ne
on the collective flow of hadrons, which can be used to perform quantitative
tests of the hydrodynamic QGP paradigm. In particular, we predict that the
elliptic flow of $^{20}$Ne$^{20}$Ne collisions is enhanced by as much as
1.170(8)$_{\rm stat.}$(30)$_{\rm syst.}$ for NLEFT and 1.139(6)$_{\rm
stat.}$(39)$_{\rm syst.}$ for PGCM relative to $^{16}$O$^{16}$O collisions for
the 1% most central events. At the same time, theoretical uncertainties largely
cancel when studying relative variations of observables between two systems.
This demonstrates a method based on experiments with two light-ion species for
precision characterizations of the collective dynamics and its emergence in a
small system.
