Custom Ranks overridden by Group Rank when setting default.

I have issue with the "Make Group Default for Member".

Basically, I often have to do the "Make Group Default" option to set things right. When I do this (for a whole group for example), it erases all custom ranks for all users.

Every so often I will make everyone in the Registered Users group the default, then go over and put the mods and admins in their groups by default.

When I go back and check all the ranks are reset to their defaults, not custom ones. What I propose is to ignore setting default ranks when a user has a "Special Rank" which is not a default group rank. That would allow for a rank to change from the default rank of one group, to the default rank of another group.. but prevent the changing of rank when a custom rank has already been assigned.

This may be a feature request, but I think it is a bug. Looking at the function "remove_default_rank" I see that it appears as if this is the actual intended function.. it however does not work as I described.