We had a similar thought several months ago, and had a machinist look at it. He did, came back and said don't. Reasons given were likely having to shave too much metal off to get the adapter to fit might weaken it too much, issue of gas vs liquid feed, and potential liability issues.
There's some pretty creative people here who might be able to tinker and get an ultralight safe version to work (Bill F. you there?), but the existing steel canisters don't weigh that much for what you use.
(FYI we boiled water for 10 trekkers for 10 days @ 1 cooked meal per day on two one lb steel canisters)
Who knows, maybe Coleman will make a Pocket Rocket equivalent ultralight weight version.