it do not matter how long it take, some games stop too early and leave us in our hunger. but the base of the game is already set. the coding and the mechanic is already there. adding content is not that hard from there. scripting events and adding new mechanic is a bit harder. but if it's just adding a new girl, you can always copy-paste the coding of one of the existing girls. change the art and tweak the lines and you get a new girl. it wouldn't even be a day of work if there is no special event associated to the girl. it's the art that might take longer as it require a lot of work.
but as long the game is working and stable, it do not matter how many up-date the game can take, each up-date actually renew the gameplay and since the game already have a lot of content, you can always find satisfaction in it.
		
		
	 
Basically, your ideas have as a base that this game has a coding on the level with the art.
Unfortunately, most artists are not good at coding, and those that create these porn games mostly make it more to put their art into than as an actual game. The creator is clearly an artist that sees the coding as a bonus at best, necessary evil at worse.
I did not look into the code itself, but I am not surprised that the ones that did claim it is badly-done and that the dialogue data is spread all around.
This is not the only game that is so.
Another work often compared to this one, Something Unlimited, also has a creator focused on the art. Its code is so bad it is MUCH heavier than it has any right to be, and its save system has the data 
on the windows register instead of a file.
There was a time he claimed to be looking for a coder to make it run better, but he changed his mind. And the reason is clear to me: he makes his game using an Unity extension that makes it much easier, but if the code was improved it is very likely this would not be useable anymore and he would need to keep hiring the coder.