list manipulation - Handy / flexible directory tree operations

Is there any shorter / more handy / more flexible way to get directory tree as a nested Rules/Associations list?

I tried to incorporate FileNames + GatherBy and GroupBy, but nothing was as short and handy as old fashioned:

ClearAll @ filesInDir;

filesInDir[dirname_, deep_] :=  If[
    DirectoryQ[dirname],
    FileBaseName[ dirname] -> (
          If[   deep == 1, 
                FileNameTake[#, -1], 
                filesInDir[#, deep - 1]
            ] & /@ FileNames["*", dirname]),
    FileNameTake[dirname, -1]
];



filesInDir[$UserBaseDirectory, 2]

"Mathematica" -> {"ApplicationData" -> {"CCompilerDriver", "CloudObject", "CUDALink", "Parallel"}, "Applications" -> {...}, "Autoload" -> {...}, "FrontEnd" -> {"init.m"}, "Kernel" -> {"init.m"}, "Licensing" -> {}, "Paclets" -> {"Configuration", "Repository", "Temporary"}, "SystemFiles" -> {"CharacterEncodings", "FrontEnd", "Kernel", "SpellingDictionaries"}}

And now, from this nested rules I want to go back to the output of:

FileNameSplit /@ FileNames["*", $UserBaseDirectory, 2]

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p.s.

I've chosen nested lists/associations to reduce ByteCount and make querying more user friendly. But if you can convince me I should keep a full paths list it would be a valid answer too.