Locos do need a short wheelbase. The Hornby 0-4-0's are ideal. Tension lock wide type couplings work well if one only uses a single hook at one end of each vehicle and removes the hook from the other end.
It is a fun concept where anything goes. Make it wild and wacky, or make it a believeable concept. It is up to you. Just keep it cheap, small and fun and you can't go wrong.

Now go build
