Now that lightroom has masking advanced enough to take advantage of it, it would be nice if we could get a simple slider or set of sliders to add blur that looks like authentic defocus blur added directly to lightroom.
Adding the global lens blur function is a good first step, but adding it globally is kind of counterintuitive.
The Lens Blur tool is by default a local adjustment since the focal plane has to be selected. However, we cannot take advantage of all local masking tools.
So to make it right I think, this tool should be split into two separate functions:
New Range mask that creates a depth map (not only like the existing one, that relies on embedded depth maps in the photo)
Local blur tool to add a blur effect to the selected mask
This would make the Depth Mask also available for other kind of local adjustments and the blur tool can also be used in conjunction with the other mask options, like Sky-, People- or Object-selection.