I think it's doable. I may be able to put in a system where only the Goblin Lord can impregnate the captured girls (like setting up a random chance of impregnation everytime you do the sex scene in the dungeon) without needing the other gobbos for it.
As for having goblin females. I dunno, man

. I'm trying to base this game more on copying Goblin Slayer setting. Which means goblins are only male gender and they'd need to breed with human females to multiply their numbers.
If enough people ask for female gobbos. I dunno. We'll see.
And goblin raiding parties is actually one of the planned benefits that you read on the post about impregnation and birthing. But I'm still thinking of new benefits of goblin raiding parties other than making gold. Maybe gobbos bringing in a new girl or something