I’d find that really useful, because due to Rhino never telling me how it Trimmed something, I now always, always use a Fin that is manually extended to trim with instead of curves. Having to skip the manual extending part would be nice (although if Rhino had explicit Direction options for trimming, it would be even nicer).
Is this part of the trim-direction kerffufle? Greg made some changes in V7 so that a curve within tolerance of a surface is used directly and overrides any direction stuff - that should sort out many if not all of the problems you’re seeing.