I'd love to see more interactive toys for the kitty cats. Maybe create a HUD, and you can just load the toys into the HUD. Little things like a dangly feather, little balls of fuzz (my real cats's favorite), a laser.
How about a script creators can drop into their creations? Maybe with an API to select the behavior such 'attract to <pos>' 'crawl/play' 'sit/play' 'scratch' 'meow' ... creators could then do scripted behaviors such as "attract to <pos>" "wait 5" "meow" "scratch" "wait 3" "walk away"
I'd love a cat-bed where they do that threading/kneading pillow thingie, a brush and most definitely a litter box!
and maybe a plant they nibble and barf after - no wait, that's too much of a RL experience
