Rarity Tied Spawner (RTS) is a mod for HBS's Battletech computer game. It is a small, focused mod with a single purpose - adjusting the rarity of units based on their tags. The mod's homepage is https://github.com/BlueWinds/RarityTiedSpawner, where you can always find the most up to date source code.
RTS is distributed under the GNU General Public License v3.0 license. Special permission is granted to Battletech Advanced: 3062 and Roguetech to distribute this alongside Custom Bundle and other proprietary code. Please reach out to BlueWinds on github, or the BTA/RogueTech discords for more details.
In settings.json, moreCommonTags is a dictionary of tags, mapping each to an integer.
When the game spawns random units for a lance, it makes a list of all units that match the lance's tags. For each unit, RTS then calculates a toAdd value based on its tags, and pushes that many copies of the unit onto the list.
Think of it as a bunch of raffle tickets in a hat. If a unit matches a tag in moreCommonTags, then RTS puts additional copies of that unit into the hat the game pulls from. Simple.
toAdd can be negative in the configuration, but the total can never go below 0. "unit_never_spawn": -1000 will not remove the initial copy of a unit from the list, but it will counteract any other moreCommonTags the unit might also have.