I know arena is an important thing in this game because in come, but is a decision you make, I do not know when users decided that arena expansion was the top priority, because you can expand little and modify prices a lot.
Example :
Check this team arena:
(181561)This guy managed to keep a small expansion but be competitive with nice income, inverting almost 2million less than other teams in his same division and getting incomes only 10 k to 20 k under them.
That say, what I think is more important than a faster way to expand arena, is make the prices changes more friendly.