I remember being in middle school thinking "hey what if engineer had a dispenser alternative like how there's a mini sentry" and the dog is a perfect idea. the dog could (instead of generating ammo/health) go get the actual pickups in the map and bring them to who ever is low on supplies /health. then there could be other stuff like hes basically a payload but can be killed and can follow you. another idea a close friend of mine had to add was: he could upgrade health pickups or they spawn faster from the ones he picks up. all of this is just spitballing but if you read this thank you.