What's an ex-US President to do?

The Times of India published this item about the impending departure of Robert Blackwill, the current U.S. Ambassador to India, and asked its readers to give their thoughts on whether Bill Clinton should be the next ambassador, since it’s well known how much Clinton loves India. The answers are interesting, and some are very amusing. A number of people suggest that a former U.S. President should not “step down” to become an ambassador… that taking such a position would somehow be beneath him.

So then… What should a former president do when his time is over? With the exception of Jimmy Carter, most recent presidents were happy to more or less retire and just spend their time giving speeches. However, Bill Clinton is still a young-ish man (will turn 57 this year). George Jr. will also be, whenever he ends up leaving office (same age as Clinton). So what should they do? Would another public sector job of any sort be acceptable?* Or should they stay in the private sector, so as not to be a “distraction” to the incumbent administration?
[sub]* I’m not talking about occasionally acting as a special envoy of some kind, as I think Jimmy Carter has done, because it’s clear that such actions are intended to be very limited in scope and duration. I’m talking about a regular, full-time position, in which the ex-pres would answer to the higher-ups just like anyone else.[/sub]

This question, as to former President Clinton in particular, was the cover article in the March issue of The Atlantic Monthly:

A few former presidents have returned to public service. J.Q. Adams served in the House of Representatives. Andrew Johnson served in the Senate. Herbert Hoover, at President Truman’s request, chaired a commission that reorganized the excutive branch, which to this day is usually called the “Hoover Commission.” Adams and Johnson, as legislators, did not answers to their successors; arguably Hoover did, but his commission was an advisory body, not a policymaking one, so the point is probably moot.

Millard Fillmore, Ulysses Grant, and Grover Cleveland, after a term out of office, sought another term; only Cleveland–who, unlike Fillmore and Grant, had actually run and been defeated for relection–succeeded. Teddy Roosevelt asked President Wilson for a military command as the United States entered World War I, but Wilson refused; if Roosevelt had gotten the commission, though, he certainly would have been his successor’s military subordinate. There were rumors during the 1980 Republican national convention that nominee Ronald Reagan was considering former President Ford as his running mate.

Nowadays, the Former Presidents Act treats being an ex-president as practically a full-time job, providing a salary, office space, and staff for life, and security for a decade after leaving office.