Yes big maps it's cool but content must come aswell with.
Fortuna is a good example, I would love to play more on it but once you have finish everything to do on these maps you have no more reason to come back except for events. This would be cool if they added end game content like relics or kuva flood on these.
+ the missions on fortuna are always in the same place while the map it's huge, you almost use only 50% of it for these interactions. So if they add a bigger map than that I really hope they will improve on the interactions content on it.