President William Howard Taft, the 27th President, actually did that. 8-years after he ceased to be President, in 1913, he was appointed as Chief Justice. Obama has been out of office for 4.
A better model would be the ‘unofficial’ roving diplomat role played by Ulysses S. Grant.
I just have a feeling that Biden WILL WANT Obama involved in some capacity. What do YOU think?
Search ‘Biden’ & ‘Obama’.