While at the LA Pen Show last month, I went to a talk given by Susan Wirth. She doesn't like any of the "boutique" inks for vintage pens (saying that they make inks that look pretty, but may not work the greatest in your pen). She does, however, like Pilot Iroshizuku because it is made by a company that also makes pens.
This is a ridiculous argument. She may be right or wrong, I am not making that judgement, but "Because they make pens" tells you NOTHING at all.
If she had a comment about ink chemistry, about staining, about pigments, or something, I'd be more willing to take her point. But Noodler's, for only ONE example, has a wide variety of ink recipes.
BSB is the notorious bad boy and I would not recommend that for anything but a standard CC pen as the Bay State line's chemistry is so different, but it is absolutely not reprentative of even Noodler's lineup, much less all of the newer brands. For instance, Noodler's also makes some cellulose reactive inks, some pretty run of the mill inks, some weird inks like Whaleman's Sepia, and some that will never come off of anything like Kung te Cheng. You treat each ink separately, taking Nathan's advice to not put Kung te Cheng in anything nice and not worrying at all with the more normal formula inks.
Anyway, in light of that rant, I don't think BSIAR is a pen destroyer. I've used it and continue to keep it in an esterbrook. It takes longer to clean than some other inks, but no biggie. I have used three Iroshizuku inks in vintage pens and don't think twice about them. I actually didn't know they were alkaline, so this thread has taught me something. A normal flush should be just fine when changing to a different ink from iroshizuku, regardless.
I don't have personal experience with DeAtrementis, but the Diamine samples I've used have come clean just fine.
Red inks are generally harder to get out of a pen than others. I had a J Herbin red in an old Watermans, flushed, flushed, flushed, and finally got it to run clear. But then I put in some Sailor blue and got blurple. A really COOL blurple, but it didn't run true to the Sailor blue until the second fill of the pen a week later. I guess there was STILL some red in the nooks of the feed, but the pen isn't harmed in any way. That pen has no ink window, though, so I don't know if the interior is stained.