There's always risk when ordering from a DNM. Luckily with r/DNM we as a community are able to quickly point out suspicious activity whether it's a vendor or an entire marketplace.
However, I'm sure there are ways to automate some of this by monitoring vendors across multiple markets to look for signs they might be exit scamming, compromised, AWOL, etc.
Here's a few indidicators off the top of my head.
PGP Key changes on one account but not others
PGP Key changes on any accounts (Keep entire history of PGP key changes?)
Increase of negative/neutral reviews on any market
Vendor inactivity or account status change (Vacation, Banned, etc)
Links and snippets of r/DNM and forum posts with vendor name references, monitor for keywords e.g. scam, exit
There's probably a lot more than can be done but I'm not entirely sure how far is too far.
Good luck getting the site owners of the DNMs to cooperate. A bot could be created to look out for these things, but it'd be incredibly complicated and I doubt anyone would code one without monetary compensation.