He would fail miserably at a small team. He can't take defeat- he sulks after a defeat... and every Everton or Cardiff of the world WILL get some defeats. He also only buys whoever is making headlines at the time- he doesn't know how to find a gem in the rough. He knows how to manage a team, no doubts about that, but he doesn't know how to build one. Smaller teams need someone who can build for the future- not just someone who knows how to rip people from the headlines.
He'll go and manage Portugal probably. Think he's always said he wanted to manage them at some point once he's done with club management.
He did very well at Porto...but only big money teams or already established and expensive squads since then. I'd like to see him go back for a new challenge - it must get boring buying trophies everywhere and then finding excuses for not winning.
He did... but Porto were a big fish in a small pond already. They had the right talent and players ready for Mourinho to use. He's a great coach- but his stints at various countries shows he doesn't really pick the unexpected- his transfer targets revolve around whoever is in the headlines. He never picks a "who's that?" player that turns out to be a gem. He buys very few youth players- players for the future... clubs he leaves tend to have a "gap" left behind once he's gone. A Cardiff or Everton couldn't survive if he left them with no future players and only aging "headline" players that are demanding high wages so the team can't afford to bring in new players. I think a national team would work out great for him- where he can coach the brightest players a country has to offer- without ruining their future in the process. No transfers- and big names. Perfect combination for Mourinho.