Heya! Glad you like the game!
The reason that we don't have many traditional RPG systems is we intentionally want to avoid any sort of grinding. We know there's a balance that can be hit between progression and no grind, and we're hoping we can get there.
We also try to put a lot of emphasis on equipment rather than character in terms of customization, but there admitedly isn't many options in terms of progression. We'll be looking into ways to introduce fun progression without grind like being able to upgrade equipment stats / abilities, but it's not a high priority at the moment.
In the current build of the game, you can change equipped gear of all party members by opening the inventory screen and clicking the near the name of the character. You just can't share items between members which is another low priority thing that needs to eventually be added.
Having more to do in the slums would be awesome, but we currently don't have any plans for it and we know that other areas are sorely lacking in terms of content as well.
When it comes to unlocking sex scenes it's currently a one or the other thing, but your gallery save is global across all saves so it is possible to do multiple playthroughs to get every scene. You can alternatively type Gallery.UnlockAll into the ingame console to unlock all the scenes right away if you don't want to grind for them.
Right now our main priority is adding story to the game, both side storylines and the main storyline. Whatever they require is usually what we work on month to month along with little improvements we can make here and there.
Hope that clears things up for you! ❤