How about the public companies themselves (rather than investors) put the money into private companies in related sectors, via M&A or venture arms? This certainly paid off for Yahoo when it bought a chunk of Alibaba.
Not sure it's wise to put the money back into investors hands where there's less domain knowledge than in the companies the money came from.
Matt Levine with one of the most clever lines (as often) regarding the changing valuation dynamics:
"The public stock markets are increasingly about capital return rather than capital raising."