Hello,
Another feature I have in mind is what could be called "Effects applied history". I imagine it as a floating list of all effects applied to the picture being edited, each with plugin parameters' values used. For instance if I applied Gaussian Blur with radius of 8 a new entry in the history would show up saying "Gaussian Blur; Radius=8". If I clicked (doubeclicked or whatever) this entry later, the same effect with the same parameter value (radius of 8) would be applied to current layer/ selection. Or other way. If I clicked the entry, plugin window would appear with all the plugin parameter values initialised from the history entry.
Regards,
Jakub "Bwana" Sawczuk