GO FOR IT! I'd love to see somebody get that working reliably inside a plugin. I still think it's impossible (at least to maintain it over various upgrades to the engine and game DLL files) since you assume that you know what is contained in the CBaseEntity and CBasePlayer classes based on what's in the SDK. There is nothing that forces MOD authors to use either of these classes as they exist in the SDK (MODs can add or remove stuff from them without your knowledge and this will break things because function pointers and member variables won't match up anymore).
BUT HEY! Give it a shot and see what you can do!
botman