I think something cool that could be added is a garden, planting stuff like carrots or potatoes and selling them for coins could be fun! And different colored coats for the cats!!
I'm not sure if this is a fault on my end, but sometimes the messages that pop up on screen like "____ is heading out now." arrive late, a cat could have come in or left and I wouldn't see the message saying so until seconds or almost a minute later, not sure whats wrong :(
If you have four adopted cats and four toys then strays won't arrive until you buy more toys. If you have eight boxes, your four adopted cats take up four boxes, so only four more strays can arrive. If it isn't that, maybe refill food!