First thing to do is, updating the GalaxyScenarioDef.galaxyScenarioDef file.

if you made any changes there. update it also into the galaxy forge folder (where the galaxy forge exe is)

but as far as i know the races are hardcoded, even if you change the race of a player (which should affect the AI players race) if you start it random it is random.

only the tutorial maps work with preselected races.

I hope the devs will change this some day...

How'd you change galaxyscenario def? You pretty much have to add everything.. the race template, the default homeplanet template, all the unit listings, etc.

You need to edit the English.str file and the GalaxyScenarioDef file

From the 7DS English.str file:

StringInfo
 ID "IDS_PLAYERRACENAME_TECH"
 Value "TEC"
StringInfo
 ID "IDS_PLAYERRACENAME_PSI"
 Value "Advent"
StringInfo
 ID "IDS_PLAYERRACENAME_PHASE"
 Value "Vasari"
StringInfo
 ID "IDS_PLAYERRACENAME_PIRATE"
 Value "Pirate"
StringInfo
 ID "IDS_PLAYERRACENAME_ATLANTIAN"
 Value "Atlantian"
StringInfo
 ID "IDS_PLAYERRACENAME_ROGUE"
 Value "Rogue"
StringInfo
 ID "IDS_PLAYERRACENAME_KOHRAH"
 Value "Kohr-Ah"
StringInfo
 ID "IDS_PLAYERRACENAME_UFO"
 Value "Arilou"
StringInfo
 ID "IDS_PLAYERRACENAME_TCA"
 Value "T.C.A."
StringInfo
 ID "IDS_PLAYERRACENAME_DARK"
 Value "The Dark"
StringInfo
 ID "IDS_PLAYERRACENAME_UNITY"
 Value "The Unity"
StringInfo
 ID "IDS_PLAYERRACENAME_EMPIRE"
 Value "Empire"
StringInfo
 ID "IDS_PLAYERRACENAME_KZERZA"
 Value "Kzer-Za"

From the 7DS GSDef file:

playerTypeCount 12
playerType
 designName "Tech"
 entityDefName "PlayerTech"
playerType
 designName "Psi"
 entityDefName "PlayerPsi"
playerType
 designName "Phase"
 entityDefName "PlayerPhase"
playerType
 designName "Rogue"
 entityDefName "PlayerRogue"
playerType
 designName "Empire"
 entityDefName "PlayerEmpire"
playerType
 designName "Atlantian"
 entityDefName "PlayerAtlantian"
playerType
 designName "TCA"
 entityDefName "PlayerTCA"
playerType
 designName "UNITY"
 entityDefName "PlayerUNITY"
playerType
 designName "DARK"
 entityDefName "PlayerDARK"
playerType
 designName "KorhAh"
 entityDefName "PlayerKorhAh"
playerType
 designName "Arilou"
 entityDefName "PlayerUFO"
playerType
 designName "Pirate"
 entityDefName "PlayerPirate"

========

Hope this helps you out.  Give 7DS mad props