My concern would be about what could potentially be lost.
Just a matter of
balancing ...
Nobody ever said that the "Expeditions"
should or
would be
as efficient as a
Colony.
e.g:
1. They would get less Yields per Turn. (Balancing of Profession)
2. They would need Equipment that costs money. (And Professions inside the City do not.)
3. They need time to walk to the spot and back. (And could be attacked by an Enemy)
4. They do not get bonusses from Liberty Bells, Health, ...
I would only use them in situations where founding a colony would not make sense.
(e.g. around a Monastery or Ford or too far away from your main colonies to later defend.)
----
Yes, the Colonist in the City needs Food.
But that is easy to consider in balancing as well.
----
Everything else would be
really bad strategy.
Because the Colonist would be
more valuable inside the City.
In real gameplay you
might maybe have
3 or 4 of
these Expeditions in
late game.
Compared to
probably 30+ Cities if you play wide.
----
Summary:
It is always the same ... players always assume the worst ...
Suddenly this new feature completely unbalanced and overpowered features will destroy all logical gameplay ...
After they get the feature and could try it, then they suddenly love it ...