It does not take any hand waving -- you're trying to redefine a standard variable. U-3 is the 'headline' unemployment number which is near 5% right now. There are plenty of other ways to calculate it, including at least 5 published by the BLS. All of them tell the same story: people who want jobs, historically and barring recession, have been by and large able to get them, even if the job itself is not ideal.

Your 50% number is more commonly called the 'labor force participation rate' and it's near 63% right now [1], but has trended down for the past few decades. I would argue (as Keynes did) that if work force participation falls and standards of living continues to rise (or stay flat) then society is having good results.

[1] http://www.cnsnews.com/news/article/susan-jones/94333000-not...

U3 has political value, but from say a military standpoint it's not that useful. The reality is the employment rate is not 1 - U3.

Further just looking at the published unemployment rate in the US there has been several changes to the definition over time. On top of that other countries use different metrics. So no you can point to U3 and call it a day.