Update and new effect included : The Warp Blur
http://doker.toya.net.pl/Blurs.dll
I'll try to adapt to your 'requirements'.
And I also have some considerations...
like for ex. the the EffectSourceSurface is still not accessable in initdialogfromtoken and inittoken methods what made me to hack a little bit (Form visiblity state change).
The Quality slider works a bit differently the the max steps. Check it and it's not "render render" quality but algorithm render quality.
I used the Bilinear cos it has Wraps option which made my life easier.
And the plugin is so slow due to extreme use of trigonometric functions:
two for every sample made to blur the pixel. ex =30 samples per pixer * 600 pixels per line * 400 lines * powerof {cos, sin, asin}
Speaking of the dialog not setting up form the token, i'll check what i did wrong.