Hello, about solar systems that have only one gas giant (or 2) and that one can not colonize, is it possible for space stations (or starbases) to have a harvesting system of deuterium?

This is feasible, but it is not currently a planned feature. Right now, the only consistent way to harvest deuterium is with facilities built at colonies. Ships with fuel reserves that are below maximum capacity may also gather deuterium from sectors with gas giants or nebulae, but only until the on-board reserves are at full capacity again. Typically, this only happens when a ship has traveled beyond its maximum range, though it could also happen if the global Deuterium reserves bottom out.

I take an example of a system that can not colonize. I may have to propose another idea:
That of adding an additional function to be able to colonize asteroids with a colony ship.

In some STAR TREK episodes, asteroids are used as bases (Nausicans), camps (Dominion in DS9), colonies (Talaxians in VOYAGER)...etc

We won't allow colonizing of asteroids, but since you can build a station in any sector, it would be pretty easy to have an "Asteroid Base" station that can only be built in systems with asteroid belts.

"Base Asteroid", yes good idea!! A kind outpost which would function "raw materials mining station" for these asteroid belts. What do you think?

The case of the gas giants and moons is somewhat different. Mike, forgive me if i talk about but I think we should consider all possible contingencies for these cases of isolated planetary bodies. We already know that the ships can come to re-supply deuterium when their reserves are insufficient.

- In my previous post I spoke of stations that could collect deuterium. These stations could increase the reserves of deuterium (and raw materials of asteroid belts) of a empire in this kind of system.

- In these cases below, the moons could contain exploitable reserves of raw materials (or dilithium).