I'm amazed that people still bring this up. Have any of you read the OP?
"If 50% of your members are active (5+ games per month), you will get full points" - this line means that you're essentially allowed to keep half of your clan members completely inactive and still receive max points for activity. Yeah, that's your "inactive rank" with the exception that we don't force you to strictly moderate your roster.

With the way it's done now clans are saved from fiddling around with members' ranks every time some of them go inactive or return from inactivity and just allow half of clan members to be inactive no matter what. Instead, what you're asking for is to be able to explicitly list people who you think are inactive and only exclude them from the check while treating everyone else as active? How is that better? There would still be limitations on how many members you can have assigned to "inactive" rank (which would still be these 50% of total member count), and then we'd also have to only give full activity points if all other clan members are active (because you already defined which players of your clan are inactive, right? everyone else must be active in that case). What's the change then? To me it sounds like more manual (and useless) labor for clan leads with no actual difference.