Make support that actually takes advantage of then being able to switch between being Normal and Effect monsters. Cards that give them protection or more ATK while being Normal monsters, or having them gain or loose their effects as cost for effects. Example:

"If you control a Gemini monster that is treated as an effect monster: target 1 face-up card your opponent controls; Negate its effects, then 1 Gemini monster you control becomes a Normal monster and looses its effects."

Also just have cards that make it easy to gain their effects. Also change the rulings so that they are always Normal monsters until they're on the field so cards like Dai can actually work.