In colloquial German, you can say something to the effect of
Would it be an idea to move the bike shed a bit to the left?
and it is immediately understood that "an idea" is supposed to mean "a good idea".
I tend to use this "an idea" in my English conversations as well, but I am unsure about its validity. Sure, it's never a problem to understand what is meant, but is it commonly used and good style?
Googling seems to suggest that it indeed is valid and relatively broadly used. Is this true? Is it, like in German, a more colloquial thing?
Edit: Note that I am specifically asking about the use of "an idea" instead of "a good idea".