If you got the clown loaches, they would need to be the only bottom-dweller, not because they're mean but because they get big (a good 16 inches max, if memory serves) and because they need a school. I'm told they get along fine with plecos, though it would end up needing a cave off the ground. I wouldn't mix gouramis except perhaps in the case of honeys and pearls, though even that's touchy at best. The shark would probably do well, except for the fact that they tend to hang out near the bottom and so could clash with the loaches. Also, if the BPs have the traditional upside-down-triangle mouth, they will have a difficult time biting to defend themselves from the shark or convicts. I really don't know much about the catfish.
EDIT: Just realized that gouramis might be too small and slow to mix well with those other fish.