Varoufakis is a very good economist but I don't think he is a good politician so I suspect that if he is leading this new party then it will not be very successful. In many people's eyes he was responsible for the failure to negotiate a better deal for Greece with its creditors after Syriza came to power so, rightly or wrongly, he is carrying a lot of baggage.
His ideas on taxation have merit. The US economist Arthur Laffer has become associated with a phenomenon now known as the Laffer curve
which tries to relate revenue received and rate of taxation. The exact form of the curve is unknown but the concept is simple to understand. If you start with a 0 % rate of taxation then you obviously get €0 revenue. If you now start to increase the rate above 0 % the revenue increases. Suppose, however, you imposed a 100 % rate of taxation. I think it is pretty certain that nobody would work, or at least not openly, so at 100 % rate revenue must again fall to €0. Clearly there must be a rate of taxation where revenue peaks and then starts to fall. If Greece is operating at a rate above the peak, and there is some evidence that it is, then reducing the rate could actually increase revenue. Will it work? I have no idea.
The Laffer curve is based on the elasticity of income. Basically if you raise the rate of taxation income vanishes so even though the rate is higher the amount being taxed is lower and you get lower revenue. The income vanishing may be quite genuine and legal. Imagine someone has a basic income of €24,000 per year and overtime income of €12,000 per year. He gets €12,000 tax free and pays 20 % tax on the rest. Now suppose the government introduces a higher tax band so that he still gets €12,000 tax free and pays 20 % on the next €12,000 but has to pay 40 % on the next €12,000, i.e. all his overtime. He may simply stop doing overtime. The tax rate has gone up but revenue has gone down. He might devote the time he worked overtime to investing and pay 10 % tax on his capital gains. If he is successful and manges to make €12,000 per year on his investments he has the same income but the revenue is again lower. Alternatively income may reduce through fraud, i.e. people working in the black economy and not declaring it. There can also be grey areas. The problem arises when the process is reversed. If you reduce the tax rate back to what it was before will the vanished income reappear? That is not at all clear. If the income stays vanished, reducing the tax rate could simply reduce the revenue again, i.e. increasing and reducing tax rates can act like a ratchet.
Another possibility is to scrap progressive taxation altogether and introduce a flat tax rate. People may not realise but up to the middle of the nineteenth century flat tax rates were the norm around the world. The idea of progressive taxation was first proposed by Marx and Engels in their Communist Manifesto, i.e. most people's taxation today is based on the old hated communist principles. Strangely enough the ex-Soviet block countries are the ones that tended to introduce flat taxation in place of progressive taxation when they were free of Soviet control. Estonia was the first to adopt it in 1994 followed by Russia (2001), Slovakia (2004), Georgia and Romania (2005), Macedonia and Albania (2007), the Czech Republic and Bulgaria (2008), Bosnia (2009) and Hungary (2011). Slovakia has since abandoned it in 2013 but it still has a very flat tax structure with the original flat rate of 19 % and a single higher rate of 25 % above about €34,400. Considerably less than Greece's very steep progressive tax curve. All these countries have experienced rapid growth and massive investment, something Greece badly needs. Would it work here? I have no idea but I doubt if the creditors would allow it.
His other idea of restructuring debt is also badly needed but I doubt again if the creditors will concede much in this direction. Nearly all Greece's debt is now official debt, i.e owed to the ECB, the ESM, the IMF and EU member states. I think they are less likely to allow any significant restructuring if it is proposed by Varoufakis than if the proposal comes from elsewhere. He is universally loathed by those in power following his attempted negotiation with the Eurogroup in 2015. Simply tinkering with interest rates and maturity dates will not achieve a lot since the former are already pretty low and the latter are typically very long. The only thing that would help Greece would be to cancel some of the debt and Germany will never allow that to happen.
Not sure that helps, Clio, but something to think about.