The stock oil filter is about a 15 micron level filter, and I read lately that the trans is more coarse, say 60 microns. I'm sure aftermarket inline trans filters are much better, I don't know what they are. The engine oil bypass filters are made for 2-3 microns, which is what all big rigs use, and they get 4-500,000 miles from their engines at the least. I would want a bypass filter for the engine and the trans, for long term life, to keep the fluid super clean. But those are about $40 each and good for about two years of life. Adding external filters is almost a big project, but nothing like the pre-oiler system. I think there is plenty of room in these Explorers, for a pair of filters mounted up front, and two along the side near the trans(on frame).
The typical bypass filter systems are expensive, but I found a single remote filter mount(about $50 or so) that can be used for a bypass filter, if a restrictor(.060") is created in the line to that filter. The pre-made mounts in a kit have a restrictor built into them, and the kits run $200ish and more. I haven't had an engine worthy yet of that level, but I bought most of the bits and pieces, minus hoses and fittings.