If you leave the original filter in the pan and replace the bypass with the Dieselsite filter you won't get an effective system. The cooler lines only see 10% of normal flow until the trans warms above 165°F. Before that happens 90% of what normally goes to the cooler is redirected back into the trans instead of going to the cooler. And under most conditions once the thermostat opens, cool fluid from the cooler lowers the trans temp enough so that the thermostat closes again. So most of the time there is not full flow to the cooler. Sometimes aftermarket isn't as good as OEM.
With the improved internal filter 100% of the fluid is filtered all the time.
you would get the same or better system IMO
the diesel site unit filters all of the fluid that goes in to it
unless there is a pressure issue then it bypasses (i won't bore with specs)
unlike the OEM remote filter that bypasses most of the fluid
if you leave the OEM pan you still get OEM filtration
the diesel site site unit is nice if you didn't replace your coolers
and had a tranny go out
now switching to the 08++ internal pan filter is great but it's not really "Improved" is it ? it is just using another ford "MY" part where it is not specified for use
another thing maybe Mark would comment on is the apparent fact that if you do an 08+ pan and filter unless you change the cooler lines to an 08+
you have to run the TP filter in the filter manifold otherwise the fluid will not hit the coolers ( path of least resistance and all of that )