Fortunately Smustard has the MySmustard plugin to help one track updates to their scripts, to me this already works like a validation system of sorts, kinda moot as a pure validation system for Smustard ATM since you get the scripts from Smustard in the first place.
It's the idea that counts, a master data register of the scripts out there and SU checks it (MD5 checksums verification on the server database would help) everytime it starts up, maybe even report new scripts and analyse them in a kind of SAFE MODE before running them.
I suppose it doesn't help people much that use SU offline, thus some kind of encrypted database file (with the MD5 checksums) distributed with SU for validation purposes would probably help as well. Should be easily updatable and probably wouldn't be a space hog.