The amount is hardcoded, ok, but what about the types?
The ship-types are insofar hardcoded, in that you will always start with 1 survey ship, 1 colony ship, and 1 asteroid miner. Or rather, the ships with the respective InternalName. So, you could edit the entries for them in the GC2Ships.xml. However, that would affect all ships with that InternalName, not just the starting ships.