the problem is that you don't have a list of all brick mods and the uinames associated with them
and even if you did, there will definitely be cases where multiple packs use the same uiname for one kind of brick. you wouldn't think this is an issue because it's the same brick in both packs, but then you have to consider which pack was actually active for the build
this is why RTB was able to provide the service, because they hosted a large amount of blockland's mods, and they could generate such a list