All tier 1 mercenary ships aren´t hireable in the exploration phase (Age of Expansion) anymore. I think they are immersion breaking when your civ doesn't know any aliens but can still hire mercenaries from anywhere. This disables the bazaar from early game. No changes later on. And this mod doesn´t do anything else.
You will still meet the bazaar early on and civs with discreet ability still get a tier 1 mercenary ship.