It's neither a coherent strategy nor will it bring enough voters over to their side.
You sound like one of the Blairites complaining of Corbyn's unelectability even though he nearly toppled May at the last general election and has created an unprecedented turnaround in Labour support after the disastrous tenure of Ed Miliband.
Actual poll movements seem to show that sticking to a strong program for change is paying electoral dividends, with somewhere between +10 to +15 for Labour in the polls over the last year alone.
A drift back towards conciliatory centrist rhetoric at this point seems very much ill-advised.
I'm not a huge fan of Corbyn's, nor do I honestly believe any elected UK Prime Minister will be allowed to implement the changes the country needs, but I think you're tactically off the mark in this case.