I absolutely love this idea! As someone who has lived in several countries around the world and experienced different forms of "democracy", I have to say that this method seems like a fantastic way to increase voter engagement.
It has become abundantly clear that what we think of democracy is broken and the system is in dire need of a major revamp. Democracy works best when EVERYONE has a vote, but voter apathy and political disdain has led us down a very slippery slope into a system that just doesn't work for the people. The Ancient Greeks are currently looking down upon us from the Elysian Fields and shaking their heads in disbelief and shame.
I would argue that we could create several different kinds of default in this system though. Having the default setting decided upon by the government or panel of experts is certainly a good idea, especially when technical knowledge is required on a decision (I'm thinking along the lines of a pandemic). With more and more voting being done electronically, I think you could also have the default as what a person had previously voted for whereby the voting database already knows your preferences and creates your default. If you wish to change from your default, vote!
Regardless of whether this is the best option or not, I think we can all agree that change needs to happen so that the people can become once again enchanted by politics and the decisions made in their country. Mr. Savic, you've got my vote!