This game shows decent Promise in being something entertaining. Im not particularly use to 3D animations, such as in this, but I found them easy to get use to and enjoy. 

The base building aspect is perhaps the game's most defining feature. but once a room is built, you can not remove it, to create hallways. I would suggest a Delete room button as well.

As for the lewd stuff, I... actually played for like, 5 hours until I figured out how to actually get the characters to participate in stuff, particularly, using books on them in the interaction menu.

after the first 12 hours, I learned how to min-max rooms and 'node features' of those rooms, which, also helped me to learn that each character also affects the production value. this game has a lot going on with a simple mask covering most of it.

basic suggestions:
•The ability to rename characters.
•Barracks Room.
A room that you can assign a character to, that will allow that character to roam that room, and the 8 rooms touching that room, basically a guard barracks.
•Trap room.
High cost room that allows a chance to capture invaders, just like how the spike rooms deal small damage when entered, this room will have a chance to capture that invader, Maybe requiring shackles to be in the dungeon inventory. 
•Starter Servant.
when starting a new game, allow the player to not only make their character, but a servant as well, limited to humans, as other races are locked behind the research, this will allow the player a opportunity to learn how to assign characters to rooms, interact with them, etc. could even go a step further and use this character for tutorial use.
•Delete rooms.
this I feel is exceptionally needed for invasion pathing. but all rooms must be linked, no "floating" rooms, to prevent inaccessible invasion areas.
•Dormitories/Quarters.
Not really needed, but something to fill empty rooms, vanity rooms that serve no purpose, maybe raise happiness/likability? or something? I mean, the master has his own chamber, why shouldn't the servants have a in-world place of dwelling, even if they do, technically work 24/7.•Mouse race.
I... Just like seeing mouse girls and boys in games ahaha.

I agree with everything you wrote except I think the starting companions of a bound hobgoblin and imp is cool. I'd like to add that the perhaps adding special invaders, like thieves who can bypass traps, paladins resistant to lust, sorcerers who conjure an antagonist to fight for and before them, and I am sure we can think of many more varieties to spice things up in the later stages.I also think the invaders should avail themselves of whatever the room they are in has when they win combat -- healing & bandages in infirmary, food in farm, gold in gold mines, etc. just like they do in the stockroom. Right now I am running 3 thematic dungeons: en elven, a koboldian, and a cyclopean dungeon. Each built around a theme and very different from each other. With the addition of more types of rooms more thematic dungeons can be devised.