> forgive me, but this strikes me as FUD.  We're talking about adding a read-only copy, not mixing many writable files.  I can't see that the API presents any hazard to the proposed usage.
> 
It might be, but although I can't point to any concrete case right now I think we've had cases suggesting that one or more OS makes a mess of keeping the two separate. There's some ugly code in the vanilla file plugin (which might not be used code anymore, come to think of it) where wild guesses are made as to whether an fpos is being done in a way that implies a need to do some fudge to force a buffer flush, for example. I'm inclined to se that as evidence of a worrying API. 

But we all know that I worry about things that don't always need to be worried about. 
/tim
{insert witticism here}