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a couple of things to keep in mind, since i've researched this a bit before:
temperatures.... they are quite important to consider. the cat WILL heat the exhaust if it's operating correctly, so should you want to draw EGR pre-cat, immediately before the cat will be the coolest location. drawing pre-cat will allow at least some unburned fuel(if any is present) to have a second chance at getting burned in the cylinder to produce any useful work from it. post-cat.... well, if the cat is working well, there should be no unburned hydrocarbons(HC-> CO and H20 reaction), so that advantage will be gone.
also, cool EGR is more dense than hot EGR, so when it's being drawn, it's a higher mass/volume.
there are at least a few US market cars made in the past 20 years that had EGR coolers... the ones that come to mind are Cadillac Northstar powered vehicles. they used engine coolant to drop the temperature of the EGR gasses before they entered the plastic intake manifold. i ASSUME that setup may have been used in other applications with plastic manifolds as well, but i can't think of any off-hand. a side-benefit of this is that if EGR is being utilized early enough, you can actually heat up the coolant faster to get your engine up to full operating temp in less time.
nothing else comes to mind that hasn't been discussed yet other than the desire for intelligent control of EGR... depending on what sensors are already present, you could impliment something as simple as a schmitt trigger(or just a plain comparitor) to only allow EGR above a certain throttle opening. otherwise, you may have to get into a bit more complicated logic.
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