So wait, if Redusa never re-upped her Guild membership....
...how could she be in line to arch Venture?
shareI took it to mean that she needs to pay dues to regain her privileges and membership. As soon as she pays, she remains in line for Rusty ahead of Monarch, but at this moment in time, during this specific threat, privileges and membership are suspended, meaning Monarch can legally off her. He can't risk her deciding to pay dues in ten minutes and needs to scratch the possibility off his list.
✌🏻Go Team Venture!
Yeah, he could have offed her regardless. He's done and is currently doing tons of stuff that goes contrary to Guild bylaws.
But she is not a member of the Guild. She isn't in line to arch Venture or anyone because one of the golden rules of the show has always been one must be a Guild member to arch. Nor can she sign away a Guild privilege that she isn't entitled to because she isn't an active member of the Guild. The Guild have always been the sticklers, not The Monarch. It is odd and illogical that they would grant any highly-coveted status to a lapsed villain who is clearly not contributing to the union monetarily and who is not participating in any evil activity. She looks retired and hardly interested in anything "calamitous".
It would have made more sense if he just killed her, she was an active member of the Guild and/or 21 had not said that line. And then it gets back to Dr. Mrs. The Councilwoman Monarch Girlfriend that The Monarch and 21 were going around off the books harassing/murdering people based off an old list or something.
You're right, that would have worked better. The line complicates it. Monarch used to be a lot more of a loose cannon. He's comparably smoothed out now. It seems he's trying not to go against his wife or make things more difficult for her. He probably doesn't want to compromise her position so he's technically following guidelines with questionable means.
It's also important to remember that the Monarch is all about flair and going through pointless time wasting measures. Dr. Mrs. His Wife has the real mind for the rules. So it could be an intentional mistake to show how much the Monarch gets in his own way. His mind becomes especially clouded concerning Dr. Venture and he needs to cut down anyone in his way, even if she isn't really.
✌🏻Go Team Venture!