The point of Rotom as far as i can tell is that it inspirits devices that have a 'special motor' in them. This is mentioned in many of its pokedex entries, even so far as to say that it can only use a specific model of discontinued washing machine (this also raises questions about the origin of this motor).

But this doesn't explain its ability to inhabit devices like the pokedex since its very clear they wont have a motor like the other appliances.

I wonder if this element of Rotom's design is being lost, because looking up rotom fan-made forms show lots of cool and creative ideas, but most to none have actual motors in them.

If I were to suggest Rotom forms, I would go with;

Blender - Steel type

Garbage disposal - Poison type

Jackhammer - Ground type

Discoball - Fairy

Printer- Normal

Running Machine/ motorised combat aide? - Fighting

Not sure with Bug, Dragon, Dark, Rock and Psychic.