presetMenuForDir.mel hacking
Ever since presets were introduced to the maya attribute editor I have found the "replace/blend" menu that hangs off each preset to be mostly redundant. I've never used the "blend", always used "replace".
Thanks to yashu I have discovered that the replace/blend menu can be disabled, allowing me to simply select a preset.
You just need to add a few lines to the presetMenuForDir.mel that gets installed in the D:\Program Files\Autodesk\Maya8.5\scripts\others folder (your install may be different, but you get the idea).
Don't edit the original; make a copy into your own scripts folder and change that one. Here's my modified version. I have commented my changes (the code was lifted from one of yashu's scripts). In this version the replace/blend menu is disabled for the mia_material, but you could disable it for everything if you wanted to.