New key signatures?

[glamfolk]

I the past week I've come a very interesting concept in two completely different places:  One in a guitar piece in D harmonic minor that had Bb and C# in the key signature, and one in a hymn in D dorian that had no# or b in the key signature.  Both make perfect sense.  Should we have a whole new batch of key signatures reflecting modes or types of minor keys?  Should D dorian still have the Bb to reflect its minor-ity, even if it's not in the scale?  Should the harmonic minors have key signatures that more accurately reflect their scales?

Discuss.