OK so I saw this accomplished in a map by Siegemech, here is what im trying to do:

I want to make some units either A) Impossible to select or B) Impossible to order. I want the units to not attack anything and to not be able to do anything at all, but to still be able to be destroyed. How do I do this?

You have to have them constantly exchanging between other players.

ie.
Give all Unit X owned by True Owner at Anywhere to Temporary Owner.
Give all Unit X owned by Temporary Owner at Anywhere to True Owner.
Preserve Trigger.

Hyper triggers required.

Non-Selectable:

Falkoner.CoW.GooglePages.com/Disabled_Sprite_Effects.html

Or simply disable the unit, or you can just place sprites of the units, or give them constantly to the same player with hypers

Non-Moveable:

Constantly with hypertriggers, move or order them to the same spot.