Nobody would go bankrupt, that's a silly assertion. For starters, there would be a spending cap and those funds would be limited to serious candidates who have enough support to get on the ballot. People get on the ballot now with hardly a dime in outside spending. 

As for funding petition drives, field offices, etc, that money would be less restricted and easily funded. Primary campaigns would hardly need to be regulated at all, given that they are not competing for government positions. Most petition drives are run by volunteers and those staffers who are paid can easily be compensated under the regulated candidate contribution framework than what we have now. 

I'm not sure where your third point is coming from. I suppose you're making the case that the money will be spent one way or another. I disagree. When campaigns were more tightly regulated, we didn't spend 2 billion dollars on elections. It's self-evident that we need more regulation and less money in politics.