The potato as king of vegetables - mmmm..... perhaps something akin to making Rumplestilskin the emperor of Austria?
What is a king? People no longer see kings as divine and untouchable; the expectation of a king is that he will be a symbol of unity, purpose and harmony, a foundation for the identity of the people; he will be responsible in some measure for guidance, welfare and justice. Kings don't have to be remote and grand - the most successful and best loved of kings have had the admiration of their people and were recognised as being "at one" with their subjects.
The potato provides a backbone for many a simple meal, and when robed and crowned with the appropriate spices and sauces, can be an adornment to elaborate ones too. It provides easily digestible nourishment, is available widely across the face of the earth in many different climates, and is relatively inexpensive - fair parallels to the king's responsibilities for welfare and justice. The potato has been adopted by the cuisines of many cultures - illustrating, perhaps, a benign version of the imperial ambitions of kings.
I reckon the potato can be king. Long live King Potato.
As for Rumplestiltskin being King of Austria, if he is still able to spin flax into gold, he may be in demand as leader in a good many countries.