Honestly, the time for opposing austerity is largely over. The UK economy is in a relatively good position. Our yearly growth rate is 2.6%, employment is growing. Inflation is still below target, but that's more a matter for monetary policy rather than fiscal. The fiscal aim of essentially any government right now should be to get current spending (i.e., excluding capital investment) down below 2.6% (it's currently on 5.7%) so our debt to GDP ratio can return to normal. Opposing austerity was something for the 2010 election, not the 2015 and almost certainly even less the 2020 one.
What needs to be talked about now is what our growth looks like - because frankly, it's mostly concentrated in a few specific industries and classes. The lower and middle classes have seen stagnating real wages for a long time now, and it should be Labour's duty to do something about that. It has the added benefit of addressing economic competency issues - Labour needs to be the party of good growth. That's something that can win elections, because I think it's just painfully obvious to most middle class people, who form the majority of swing voters, that they haven't really seen their standard of living improve in quite some time, and it also cleaves to the core Labour values of progressivism because by making sure growth goes from the bottom up rather than vice versa, you help the poorest.
I think there's a number of ways to approach that, ranging from education reforms to improving the school-to-work transition with things like guaranteed employment schemes. Big infrastructure plans need to be undertaken, particularly house-building, to help people get onto the property ladder, and at the same time serious steps towards reforming the private rented sector so that people can make stable plans about their jobs and where they're going in life. Reforming the JSA so that unemployed people can actually make long-term plans about job-finding or further education rather than being stuck in a bureaucratic administrative system. Open pay policies to help discrimination, both well-known ones (against women and minorities), and more subtle ones like class discrimination, because diversity helps economic growth. Closing down serious tax loopholes, like non-dom rules, and shifting where the tax-burden lies so that the very wealthiest inviduals and largest corporations actually meet that burden while smaller businesses can thrive under lower tax rates. Cracking down on uncompetitive markets like the energy markets and the rail system that stifle growing businesses by charging monopolistic prices. Introducing things like state child investment bonds so that all kids can have some basic form of capital when they reach full age.
I mean, there's a huge amount of things Labour can do without going full Corbyn that can a) win elections, b) do a huge amount of good, and c) the Conservatives will never do. They're more subtle, and I guess less exciting for it, but they're there, and they're important. I actually think Ed Miliband understood quite a lot of the above; I think he was serially underrated as a leader (particularly considering what the party looks like now - he was holding all that together behind the scenes). The trouble was that he was shit at messaging and also made a massive enemy of almost all the national media very early on. We don't need a Corbyn, we need a sexy Ed Miliband.