I have heard the term "pioneering settler" before but I don't remember the context, sounds okay but in this game you might end up confusing it with the normal pioneers that are in the game already for a different function so I am not sure if that is the best word.I would suggest "pioneering settler" or "settler-pioneer" as a term. I've found it being used in a few history books using the googlefu.
"Ausgebildeter Siedlungsgründer" is a very sperrig word.
"Ausgebildeter Siedlungsgründer" does sound indeed a bit strange as it would indicate some education in the field of founding a colony. "Erfahrener Siedler" does not really fit either as that would indicate experience in founding a colony however the unit would not have any experience in founding a colony as it had not founded any colonies before. It's neither the education nor the experience that makes a colonist a settler, it's a) the stuff he has with him and b) an empowerment from the crown to found a colony.
"Empowered Settler" would be more accurate, however I sense it won't be clear to everyone what the function of an "Empowered Settler" is (same as you would not automatically know what a "Erfahrener Siedler" can do). I would instead suggest something simple like "Colony Founder". It might not sound the best, however anyone who plays the game would immediately know what the unit is good for without looking up the Colpedia. Especially bearing in mind that this city founding mechanism is new, even to people who played Colonization before. If everyone starts with a "Colony Founder", everyone knows about the unit. That way you avoid that players who are new to WTP getting frustrated by not knowing how to found their 2nd colony. If you call your starting unit "settler-pioneer" or "Erfahrene Siedler", a newbie might still miss that this is the only unit able to found a city.
