I think implrementing such a more complex system than what they already have would derail the experience of being Geralt of Rivia. I don't think he should become a known criminal for stealing some bread from some peasants. From a gameplay perspective, why would lootable items be present in a given location that you're not supposed to take but have the opportunity to? It's more of a focus which would imply there was an intent there that would allow you to become good at theft, making theft an aspect of the game. Geralt isn't a thief. He's a monster slaying adventurer.
I like how the current system sounds, at the moment. I'm not a fan of looting random things unless I need them (although I know some people are huge fans of that ~ kleptoGeralt!) so I don't think a more complex system would benefit me or the kleptomaniacs? It's a decision they made obviously. Maybe mods could help.