just a couple thoughts
The house size of 40 (with house upg lvl 5 bug only 30) seems quite short when you really want to breed superior chars, you need at least each one of the main races and if they have not perfect traits or the wanted body size, you´ll need even some more of the same race. Then you need some chars to get money for the expenses, even more in the later game. I have also a couple god like sex skill chars with terrible traits/stats, but to abandom them is not a option, they earn a lot of coins in the brothel
My thoughts are, what if we can ´sell´ the hybrids (like now in the game) to Castalia, with the option to borrow them back for a couple days - for breeding or maybe to improve the stats or add new (better) traits. With higher affection with Castalia maybe even swap them with others of the same hybrid race (example with different body sizes or genders) - if you know what I mean. So we could "store" at least one of each of the hybrid secure for further uses or needs.
About the "Selling", I see your concern about balancing the price. I think maybe set a fixed basic price for the char (depending on body size) and for each level and stat point above 0 add a fixed amount of coins (example 5 - 10g for each point above 0), also for the traits - positive traits add some coins, negative traits lower the price. Special traits give more than usual traits. Maybe you can group the traits in classes from uncommon to common to special to epic to legendary and also their prices by selling chars with them.
I have seen that (for example) a male/futa with giant size breeded with a smaller female/futa gives mostly only the smaller size for the offspring (strange thing besides - I got large chars from 2 giant breeders). What if you make the "giver" body size more important than the "reciever" size, or maybe depend it of the viril./fertil. of the giving char. Example: if the "giver" is a giant sized with 68 virility and the "reciever" is a large sized with 30 fertility then the offspring body size should be giant. If the "reciever" have a higher fertil. than the viril. of the "giver" then the offspring could get also the size one from the "reciever".
In the game is not really a good option to see your own chars stats. The Combat form screens resets everytime to medium size and stats and if your own char is a different size you have to change it in th combat form screen to see "your" chars stats.
edit: Arena Boss Battles causes the game to loop indefinitely after pressing the "Enter" button without entering the battle screen and then you have to restart the game.
edit 2: I just got my forth char with name "Elaine" - 3 of them are the same race. A name change option would be handy
edit 3: if you have more than one couple inside the farm you cant see who is breeding with whom
That´s it - like I said, just thoughts ^^
No thoughts but reality - Your drawings look awesome beautyful and incredible sexy- I really like them. Keep up your great work with the game. Imo it´s already much better than all other breeding games out there