I think an interesting idea for an update could be like, status effects for the passengers? I know that sounds a bit silly, and it kind of is, but I can see it working as a way to spice things up. Like a bloated effect, that makes passengers less appealing to other passengers due to belching a lot, or maybe a ravenous one which makes the passenger with the effect get bigger with every stop. (This could possibly require more sizes because it'd be kind of pointless for a weight stage 5 passenger.)