I have seen pumps that allow you to extract the oil out of the dipstick tube w/o needing to pull the plug from underneath. This seems great for changing the trans or transfer fluid, but I am concerned that it will not properly pump the oil pan clean and leave any residual that may have drained through the plug hole the normal way. Does anyone have experience with these or could recommend one?

This is one I saw:
http://www.griotsgarage.com/catalog....2050&SKU=10186

 

IMHO that would only be good for if you had over filled it after a change of oil.

I doubt there is any way you could get even close to draining all the oil with something like that before it started taking more air than oil.