This is what I did with my old Zeagle (just wanted to see if it would work)-- I took the Bladder off--cut the straps that string through to the Zeagle harness. Then I lined up the bladder to the BP, and marked where the holes in the BP were. After taking out the bladder, I used a Soldering Iron to melt holes on the marked areas. Then I went to the hardwear store bought some Stainless Steel Gromets and some Countersink screws and installed them. Worked great-- as a matter of fact I gave it to a friend of mine that uses it as his primary rig!
At the Long Beach Scuba show I noticed that Zeagle is making a BP design-- they kept the same design of the bladder (straps and all) but they just screwed some bolts into the thread webbing, it looked very looked hokey... I believe putting Gromits in it would be much more secure.
You will then have to replace the dump valve on the inflator to a stanard non dumping sort, and get a shorter length inflator mechinism hose, if you want it to be "DIR".