I'd say TD could definitely help the Lions out, at least in the short term. The tricky thing would be to limit the scope of his powers to strictly player personnel and bring in a guy (or gal) to see to the administration. I think where he went wrong in Buffalo was trying to oversee every little detail of the team. Anyone who would deny that he's an improvement over Matt Millen is either abusing drugs or delusional with a personal vendetta against the man.
Donahoe's only sin is that the Bills never made the playoffs under his tenure, truly a cardinal sin to the fans, but I don't think he ever made a move that he didn't think would benefit the Bills. When he took over there was crisis after crisis with the Bills, from salary cap hell to QB issues and lest we forget a growing apathy from the fanbase. At the end of the day, he left the team better than when he found it...