Why do you need a sump? What problem are you trying to solve? Saltwater or Freshwater?
If all you want to do is add some extra filtration to your freshwater tank the 10 gallon aquarium should be plenty. There are hundreds of sump build threads on here if you do a little searching. IMHO I think they are all way to complex... I would KISS...
1) Put a pump in the bottom of the 10g and plumb the outlet back into your 72g tank.
2) Add a couple of bubble wands to the bottom of the 10g and plumb them to an air pump.
3) Fill the 10g with bio balls or scrubbies.
4) (The hardest part) Craft a drip plate to sit inside the rim of the 10g with sides that extend up a few inches. (Think tupperware or Rubbermade)
5) Add a piece of filter mat on top of the drip plate.
6) Plumb your overflow to dump into the middle of the drip plate / filter mat.
I would run your new wet/dry filter with a couple of inches of water in the bottom. The Bio Balls / scrubbies that are submerged won't be as effective as the ones in the air with water trickling over them. They will keep your bacteria colony alive a lot longer than the dry ones in case of a power failure though.
Anything else you add to this design will just be for convenience. You could add a vertical partition and horizontal eggcrate to contain the bio media but this would only be to make it easier to service your pump. How often do you think you will need to service the pump anyway?
I have a commercially built sump on my 110g that I got for a good price on craigslist. It is pretty much exactly what I described above with the addition of the partition and eggcrate. I still have to take all the bioballs out to add or remove the heaters laying in the bottom under the bioballs... but the pump comes out easily
. My wet/dry is only about 8 gallons and rated at 100 gallons. A healthy part of my 8 gallon sump is taken up by the pump access so I would estimate a 10g tank full of media could easily care for a 150g tank. The filter mat is what will catch all the debris so make it as easy to access and clean as possible. IMHO the best part of a wet/dry is the huge amount of oxygen they add to the water. They are a very effective biological filters too but the oxygenation is what they excel at.
I am sure you could come up with a much more complex wet/dry design but I doubt you will come up with a more efficient one!
