That you can definitely do without doing anything to the constitution.
Yes, and back in my Taiwanese flag proposal thread, I called for people to make new flag designs that would fit under the current constitution.
The constitution only specified:
The national flag of the Republic of China shall show a red field with a blue sky and a white sun in the upper left corner.
Nothing about the dimensions or what the sun should look like. So technically any of the following flags would fit the description.
