A larger engine with more power would increase the price and weight of the bike. There are always trade offs for more power. Personally, the Wing has enough power for me.
The 1.8 liter Wing engine is basically de-tuned and capable of putting out more hp and torque. But, the engineers designed the Wing engine to last many, many miles. More power and torque (increased metal stress) from the existing Wing engine could decrease its reliable longevity. Therefore, I would think a larger engine would be required for more power to keep engine longevity a non issue. The bike is big and heavy now. A larger engine would need more space and would probably require larger and heavier accompanying parts and the bike may become too big, too heavy and too expensive for many riders.
I could probably afford the increased price, but I would not want a bigger heavier Wing.