OK then let's address each of your original points:

- Increased circulation within the pool
How do you know? Did you do a dye test with a MD on vs off and see how long it takes to get a full mixture of color. If not, you might be surprised that is not all that different. The MD may have a slight edge but by the time the pump shuts off, there is no difference. Plus properly placement of high velocity returns is far more effective at improving circulation than a low velocity MD.


- Collection of debris at the bottom near the drains
Ok, I guess if you don't have a floor cleaner, this might be useful. But again, this could be due to the slope of the floor or other factors. Have you tried turning off the MD to see if anything changes? As I mentioned before when I did this with my pool, I saw no difference in where debris collected except within a few inches of the MD. In fact with the MD on, it was more prone to getting clogged with leaves that fell near it.


- I always have circulation, regardless of how "full" the skimmer gets (I have them both cut in full at the pump)
As I mentioned before, a wall port is a better solution because as you just said in the above quote, debris collects around the MD and if you have leaves, they will clog the MD as well.


- Draining of the pool (excess water from rain, or draining to winterize) is easy
I can see this with an IG pool but with an AG pool you can just use gravity to drain the pool (e.g. siphon or side plug).


I just don't see these points as justification for adding a MD because for the most part each of your points can be accomplished in other ways without the downsides of having a bottom MD. To each his own as they say.