Thank you for these suggestions!
I agree that some additional, optional sound effects would be nice to have. I'll see what I can do!
I plan to add some mutual gainer personalities that'll both want to be fed & want to feed you up at the same time. :)
In the upcoming Dizzy's & London update, I'll be adding lots more to the underground facility. So, some of your ideas for improving this might come to fruition!
I can certainly make stretch marks an optional feature when starting a new game. I'll get that sorted in the next update.