As discussed in this thread, the only way to insert the R15 default block package without manually building it is to insert a model. This model is not guaranteed to be updated. In addition, the block package has to be handled as a special case in code since it isn’t inserted like other packages via GetAssetIdsForPackage, and doesn’t show up in GetCharacterAppearanceAsync.
The R15 block (default) package should be uploaded as an actual package – off-sale, of course – and be treated like a normal package instead of a special case in GetCharacterAppearanceAsync.
I ran into this issue yesterday when creating a utility. I had to special case blocky compared to the other packages which I wrote a generic function for. I can definitely see the use case here. I’ll see what I can do