Wait, what exactly were you asking me to source for there? I had thought you were asking for references for why I don't think the Flowers would look fondly on frivolous use of plotholes and other PPC technology, but the story you linked seems to instead be concerned with Vemi being plucked from World One and temporarily turned into a Mary Sue, which was, judging by her summary on the wiki, due to partially-conscious reality-warping Maia powers and not due to plotholes or the Bridge. Also, it spawned several pop-up ads, which are unrelated to the story but were not pleasant. Did you mean to link something else?
I think the SIELU name may have been a holdover from when they were first introduced, which was back in the early years before the system and of Departments and Divisions to those Departments was fully stabilized. I can't say so for certain, because I wasn't around then, but it seems to imply in the first mission's text that they exist outside the usual Department framework, simply existing to sort out elf-related issues, which possibly means that "Interdepartmental" references their ability to take on missions that would otherwise be covered by any number of other Departments, as long as elven culture is being messed with during the offending badfic. Since, to my knowledge, Floaters was not officially a department yet at the time of SIELU's creation, and only existed in the lowercase form as the subject of occasional references, i.e. Since Upstairs couldn't really assign Alice to any one Department because of her limitations, they made her a "floater" instead. from the third Architeuthis mission, the "Interdepartmental" label existed to cover what "Floaters" would come to mean later. On that note, this explanation also justifies why SIELU would be labelled as part of Floaters in the wiki's List of Departments(though I can't recall any written works explicitly confirming or denying that).
Also, this line: The whole new unit consisted of Unit Head, The Poison Ivy in bright pink dress, and herself. in the first mission seems to indicate that Alec may have been assigned as Lambda's partner in the second mission simply because there were no other SIELU members. Maybe the Poison Ivy wanted to either prepare her for a multiple-agent model for when someone else takes a SIELU job or to keep her from responding to the misplaced flora and fauna of her second mission with a flamethrower, but with exactly one mission with one partner and one mission solo, neither of our deductions have a lot of examples to draw from.
Also, on an unrelated note, that SIELU Mission 1 quote had some shoddy phrasing; unless the Poison Ivy wasn't actually the Head, and the real Plant in charge was never seen, that sentence should have been structured differently. It's things like that and the distracting black-and-red alternating text in the second mission that made me not enjoy reading the SIELU missions. They were entertaining, to some extent, but I just didn't enjoy reading them.
The DOOCH? How long has Agent Huinesoron's new partner been around? The last time I heard of anything involving the DOOCH was a 2006 edition of the Multiverse Monitor, and even then it only involved someone wearing a DOOCH green uniform and not actually showing any agent activity.
Speaking of inactive Departments, in the Vemi story you linked, a character named Bjam appeared, occasionally uncapitalized in a manner consistent enough that it may or may not have been a typo. She was only ever referred to as "a morale officer" and seemed to indicate in dialogue that there was more than one person filling that role, but the wiki has practically no information on her. Since she appears in one of your interludes, you might have more information on what she did. Namely, what is a morale officer? What's the difference between what a morale officer would do and what FicPsych would do? Does the PPC have them any more after FicPsych absorbed all of the subsidiary psychological services back when the Manual was being written?