As long as you can rotate a parallel view, it won't stay isometric or dimetric which are parallel views at a specific angle.
So I don't think that Pilou's demand is feasible unless he wants a static view.

This brings a question. Would it be possible, however, to have a "Home" view choice for parallel views ?
The user could then select the "home angle" (maybe in the options) : Isometric, dimetric or even define his favorite parallel view angle.
Edit : When a user would press "Reset" in the 3d parallel window, it would zoom to the selected object (like it actualy does) and reposition the camera at that preset angle (something like Sketchup's Iso button).

By the way, thank you Michael, for your involvement in this forum.
I have used dozens of programs since the early eighties but it's the first time that I can see such a direct interaction between programmer and users.

Michel