The tweaking you suggest could be done in a legal, constitutional manner, by amendment. I highly doubt that will happen. A constitutional convention has only happened once in the US, in 1787.
My sense of all the whining is that our progressive friends want all the money that influences elections to come from the left, i.e. unions. CU merely allows any group, (unions, corporations, groups of stoners) to pool their money and spend it as they see fit.
Another observation from me: You will often see the term "buy the election" as if it is a foregone conclusion that the side that spends most on advertising wins. Spending does not necessarily garantee a win.
For example, a huge money advantage did not work very well for Eric Cantor in his reelection attempt in Virginia. His campaign spent 100 times more than his unknown opponent and he lost. Poor Eric had to take a $3M/year gig on wall street as a consolation prize; the poor guy is even more impoverished than the Clintons. Those poor, impoverished politicians!