My recommendation to mitigate concern is as follows:
1) Liberate the Trace tab from Cloned Tiles. The behaviour is based on x,y position, not row,column and can therefore be applied to any selection of objects. The functionality should probably be part of the Fill and Stroke dialog.
2) Add support for Blur to "Tracing" - support for Opacity exists so I don't think there is any reason Blur can not be supported in a similar fashion.
3) In addition to using an image, add support for a gradient (same as creating an image with a gradient, but automate the step of creating the image for the user - also remove the need to show/hide the image in this basic case). If it can be made fast enough, show a live preview of the change to the property as the gradient is being modified (e.g. show change in blur as end points for line of gradient are moved around). Note: Gamma correction and inversion would only apply if an image is used and would not be applicable for a gradient.
4) Extend support in gradient to non-linear interpolations. Currently gradients are linear - amount of change at each "step" is the same everywhere between the two endpoints, like a constant velocity. In contrast, the changes could begin slowly and an increase towards the end, like constant acceleration (or inversely, start fast and decrease, like deceleration), or the acceleration could be variable and follow a curve such as a sine curve or exponential curve.
5) For the options (hue, saturation, lightness, blur, opacity, ) evaluate whether these "Tracing" controls are sufficient to replace the (row,column) approach. If the functionality is deemed equivalent, simplify the Cloned Tiles tool by removing the functionality.
4) and 5) can probably be done in any order.
Veronika