Also, I don't recall any description of their units other than a cruiser/carrier and fighters, and infantry. I don't recall them having any land vehicles or anything else. Also I believe only like two of their planets were named.
And the biggest thing about the Ssi-Ruuk is that they entomb their prisoners. Without that ability/aspect to their gameplay, how different are they really from other factions? I don't think they're interesting enough to include in the mod, as the team would have to flesh them out completely, even more so than the EtoH. And the Chiss/EtoH (I consider them one) are much more interesting and cooler...
I think the suggestion was as a non-playable faction. As far as entechment goes, that isn't something that would really show up in the game mechanics, even just population capacity taken from other planets would technically fill that role; it's just their power source, but it's not like the other factions have to worry about reactors or something. If anything population capacity fits them better than it does any other faction. As far as needing to be fleshed out, they're far more complete on their own than 2/3 existing minor factions, and way more complete than the Empire of the Hand was when we started, which only had one fighter. The Yevetha had one fighter type and one frigate type, the Hapans two frigates and two fighters. The Ssi-Ruuvi have D'kee landers, Lw'hekk manufacturing ships (carrier), Fw'sen picket ships, Sh'ner assault carriers, Shree battlecruisers, Wurrif cruisers, Swarm droid fighters, and V'sett interceptors, all of which have a design, except the V'sett which has a description.