The hands-down best modding team for RimWorld is working on a spate of new content from the Mass Effect universe, putting the "story, races, objects, and conflicts of Mass Effect" into the sci-fi colony management and survival strategy game. The goal of the mod series is to drop the things of Mass Effect into RimWorld as though they belong there, not reskin the whole game. The core mod for RimEffect is now on the Steam Workshop, and this first of many adds... a lot.
The core mod focuses on adding the Systems Alliance as an Ultratech faction in RimWorld. That means all manner of Mass Effect-y weapons and armor show up, as well as Mass Effect styles of buildings and furniture. There's also a whole new way of building, using prefabricated panels, that makes putting up new structures a snap if you've invested time and effort into the creation of the panel elements.
You can also give your characters Omni-Tools and a suite of related tech powers, like combat drones and defense matrices. There's even Biotics, which if installed in a person as cybernetics unlock their latent abilities to toss enemies around and summon singularities and all that good Mass Effect stuff.
Finally, the mod adds two new AI Storytellers to RimWorld based on Mass Effect's rival Paragon and Renegade ethos. The Paragon Storyteller rewards you for fostering alliances with other factions, while the Renegade Storyteller rewards you for racking up enemies.
In addition to the core mod, there's an extended cut addon with bonus gear, an N7 mod with all your special operations needs, as well as interface overhaul and music mods. In the future, modules planned include Cerberus, Quarians & Geth, Salarians & Krogans, and Turians & Gangs packs.
The modding team's ethos is the same as their very well-regarded Vanilla Expanded mod series, a pile of addons that are designed to mesh with and work alongside the standard game rather than rewriting it. Thus, it should all be balanced with what's already in the game and with the other mods in the Vanilla Expanded series.