Some research papers, such as Arnold 2005, has investigated the possibility of using artificial megastructures transit signatures as long-range, long-lived and low-maintenance signals of unambiguously intelligent origin.
My question is the following:
What kind of N-body stable orbital pattern would be the most likely to be interpreted as a sign of intelligent intervention by people doing photometric (and associated) transit observations?
To provide some context, let us imagine a sentient ET civilization that has the capacity to rearrange the orbits within its own solar system and, for some reason, want to signal its existence into deep space. The technology employed doesn't allow to create fancy geometrical structures, such as toroidal planets, swarms or continuous rings, excluding clear cut transit signatures. However they can eventually channel asteroids into self-gravitating (spheroid) objects and modify planet masses through controlled collisions. The process is time consuming and incredibly difficult but in practice any N-bodies orbital configuration can be achieved (N is mainly constrained by solar system mass availability although there is also a minimal cross-section limit to consider for detectability, so 1 < N < 50 seems fair). Importantly, because of energy availability limitations, the new orbital configuration must be dynamically stable such that no future correction is needed to maintain the system in the long-range.
I am not necessarily looking for a precise configuration, but rather to explore categories of solutions. My impression is that there are two seemingly opposed approaches to the problem.
The first is to use tailored periodicities as a message carrier, in the spirit of our lighthouses, which could for instance mimic an atomic spectrum in frequency domain. The unlikeliness of this kind of orbital configuration would come from its high level of order but could also be overlooked, particularly by an automated detection procedure. Also long periods would necessitate even longer observation times to be spotted.
The second approach would be to use an overly complicated contraption of coupled orbits, triggering attention because it appears against any common sense (i.e. what is this thing?). Then, with deeper analysis from the observers, something must drive the cursor from strange to clearly unnatural. Maybe an underlying ordered signal. The risk for this kind of configuration is to be interpreted as a perturbed system in transient state.
Another formulation for this question is, what could SETI enthusiasts look for in the Kepler mission dataset?