I do not think that with your other animals, that the substrate itself is what is causing the impaction problem...unless, perhaps it's a snake ingesting large woodchip chunks while eating... If you use most types of soils and sands, the animal would not have a problem with ingesting some of it during feedings, as long as the humidity is correct/suitable.. Many people keep their animals in low-humidity enclosures, despite the true needs of the animal, usually in the form of aquaria with screen tops.. This in most cases leads to dehydration, and thus complications with passing waste properly/safely..
If you are having a problem with your animals becoming impacted with soils, sands, etc.., I would reevaluate your husbandry, and try and correct the humidity problem... Opt to go with a cover that will help hold humidity in, unlike open screen tops..
So, as far as ackies goes, if you give them proper humidity levels, to allow them to be healthy, and digest properly(temps would also play an important role in this), there should be no problems with them becoming impacted. Plus, because of their habits of excavating burrows/tunnels, etc.. I would much rather give them something to burrow and dig in, as opposed to live a boring life on top of astroturf, or newspaper... It is in their nature to burrow, why deprive that?
So, in my honest opinion, I do not think you would have a problem, if you provide them with the proper setup/conditions...I hope this helps a bit, as this is what I have seen personally with several of my animals in the past, and feel that it may help out your husbandry/health of your animals.. not just monitors.. I wish you the best of luck, and have a great day!
bob
The Odatriad