Why should XControls be different from any other control? I would argue that if this is implemented (and my personal inclination is against it, although it certainly has some points going in its favor) it should be implemented for all controls. And you would have to account for the non-icon view somehow.
In any case, it should be noted that this is already available today to some degree - the value property allows you to do this.
If setting the value is something that can cause an error, you should set that value using a custom property that you define on the XControl. FPTerminals achieve their great performance speed by being unconditional accesses to the control's value, unlike property nodes.
