One-Way Mix-Paste Cross Fade

The cross fade option while mix-pasting is great, but i would love to be able to set it to crossfade just the top or just the tail (or both like it is now) depending on the situation.

Example...

I want to mix-paste something, but want it to cross fade at the start of the paste, and be a straight cut style paste at the end of it.

I will try to explain better if that didn't make sense.