This squad is easily one of my most consistent and favorite ORAS teams, and its pretty much the only one I spammed in whichever oras smogtours I was able to participate in (also Shoka won one of his later OST games with this team without any prior experience). One characteristic of this team that makes me enjoy it so much is how versatile it can be, getting neutral to good matchups vs most squads. Reuni was obviously the focal point of my build, and I paired it with Manectric for some reason that I have now forgotten (I do remember, however, that I really wanted to avoid using MLati (I felt people were slapping it on teams without much thought)) - regardless, the duo works extremely well to to beat down on a large variety of playstyles. Reuni could use Shadow Ball to help out vs psychics like meta/mie and also hit sableye, but i've liked focus blast for its ability to hit steels a bit harder so I use that instead. Resttalk keld provides a reliable bisharp / other dark and scizor check that can last throughout the game while also placing offensive pressure, which is really good. Chople Tar is simply an amazing mon that gives me a way out vs so many major threats in this metagame like MZam, Torn, or Zard-X, and pursuit trapping for manectric and keldeo is simply perfect. TWave may be mexican, but it can be crucial in aiding a reuniclus sweep if timed right, and also provides the team some protection against BD Azumarill. SDef skarm fits pretty perfectly here, giving me an element of hazard stack while also handling a multitude of threats thanks to the special bulk and natural physical defense. Because of the support from resttalk keld (which helps against weavile alongside skarm, for example) and reuni (which can semi-handle mmeta for this team alongside skarm, for example), the reduced physical defense doesn't bother me at all. Amoonguss completes the team by providing a solid answer to offensive waters and just a plethora of stuff in general, while clear smog is extremely useful especially alongside twave support, and regen gives me a lot of freedom when playing with guss.
The only concern that has really been brought up with this team to me is the lack of hazard removal and mega sableye, but the combination of reuni + guss + my own hazards helps immensely in the hazard game when sableye is not involved (I have, for example, beaten stall by utilizing mostly just my own hazards and endless switching between reuni and amoonguss). A lot of starmie balance teams are heavily pressured by reuniclus, so the matchup issue here is rarely impossible. Sableye is also difficult but its not unreasonable to manage depending on the team support it has. Regardless, using Shadow Ball > Focus Blast on reuni solves a lot of the problems here. Otherwise, the team is very good and consistent (at least, for me), so I'm very happy with what I have.
(e: Volcanion murks this team unless you outplay it (they're gonna spam steam eruption, and if they don't, at least you can pursuit it. hazards also wear it down fast). F### Volcanion.)