I remember playing this Brood War map a a child (might also have been a mod, but I dunno), it was a campaign type map, where you start as a civilian, and you need to choose a beacon to go to. Here is an example of what would happen for when you went on a beacon: If you went onto a Zerg beacon that had Kerrigan and two hunter killers, It would give you a Zerg base as well as those units; in addition, every time you trained a Hydralisk, you would get Hunter Killeres instead. Choosing a different beacon would give you (in the same base location), that race's base, the three units, and one unit type would be replaced when you train it with its heroic version.
Does anyone know the map (or mod) name?
Could something like this be made to work in SC2?
I an super curious about the map triggers that would be used.
Never heard of this map specifically but there are plenty of such concepts on the arcade i.e. Space Zombies being the first one that comes to mind - civilian enters a region then your hero spawns.
A trigger might go like this
Event: Civilian (male) enters Any Region
-> entered region == <insert race 3 times, one for each race> Select
Local Vars: none
(General) If conditions then do actions else
=> Conditions: Entered Region == Terran Select
Create 2 Marauder at point MarauderSpawn
Create 1 Raynor (sniper) at point HeroSpawn
Create 1 Planetary Fortress at point PFSpawn
and now follow up with additional if then else's to check other race possibilities. This is definitely doable so you should give it a try. You could also then disable or hide command card buttons for the player governing what unit gets trained. Or you could have a separate hero train ability if you wanted.