Blur layer (defocus) witn loading preview textures

[hum@no.id]

I'm trying to create a blur layer over pano for loading (with preview color small res. tiles),
trying to find treatments but I think the external solutions do not achieve ...
would be very good to use internal function - together with the pre-load,
and may also be possible activate to separate this post-effect (over pano) for any creative solution...

thnx