change barline type with time signature change

[Kieren MacMillan]

Hello all!

I'm working in Lilypond v2.17.9, and the conductor of my chamber opera (being 
performed in April) wants the following stylesheet override: the default 
barline type should be dashed or dotted, but the barline should be solid (i.e., 
standard) at every time signature change.

What's the best way to do this, abstracted of course (because this is the only 
conductor who has so far requested such a thing).

Thanks!
Kieren.