A liquid democracy would have to be much closer to direct democracy than representative democracy in this regard.

In California you need to collect a certain percentage of the population's signatures to get something on the ballot, and I imagine it'd have to work the same way. You could increase the frequency to yearly, or even quarterly, and build a system where you can endorse anything you want to be added to a ballot, then once a quarter you can vote on the issues you care about, and give the rest of your voting power to any other citizen, who can do the same for any other issues.