I would personally keep the filter inside. If you get an aftermarket trans pan with a drain hole changing the filter is not very hard. going slow i can change the filter on my truck in a half hour. you have to change the ATF anyway, and the pan has to come down. you might as well just replace the filter then when you are inside.
I'm not planning on taking out the internal filter. The remote filter would be in addition to the existing and in line with the aftermarket cooler. I'm just not sure there would be anything to gain by doing this.
An aftermarket pan is something I didn't think about. I see one in the catalog that adds 2 quarts capacity and is finned for additional cooling.
i would personally just stick with an aftermarket pan and oil cooler. summit racing sells good pans, i've picked up 2 from them. i don't know much about adding extra filters, so i can't really say there.