I see where you're coming from now Ojuka. I've never seen anything in Pans Ops that justifies the selection of a lead distance of 2 NM. Indeed, my examples on page 1 suggest that there should be some sort of statement about the speed because the optimum speed for the turn does not equate well with the range of speeds for Initial Approach, particularly for Cat C/D types.
And, of course, the speed situation is much worse if the altitude involved in the manoeuvre is above the 4,000 feet that I used in my examples.
It has to be said though, that the most common usage involves a transition between Initial and Final Approach. Thus, pilots really should anticipate the need to slow down, to be able meet the speed range for Final Approach by the time they pass the FAF. Following this logic, it is probably a bit unreasonable to try to execute the turn at speeds above about 180 knots, as you say.
We can probably design a turn that caters for a larger radius, but there'd have to put a note about it on the chart because it differs from Pans Ops criteria. If we do all that, how do we provide an opportunity for pilots to slow their aircraft down for final approach? The only way is to build extra track miles into the procedure somewhere - making it longer to fly, less convenient for ATC traffic flow and more costly for aircraft operators.
I guess that we can't please everyone.