Technicality accepted. You shared some of what you learnt. :PEdited By: Kay Dallben on Year 17 Day 123 9:18
See, that's Interesting case information to share. Doesn't happen every day, and I actually mis-read the meaning of "need to change production factions" as referring to You needing to hop rather than actually needing to ditch the old faction.
No, you shouldn't need to even do that, unless maybe -- You're making Items?
The "production begin" check (ie my #2 above) has already taken place. Money deducted from the faction, RMs consumed. There's no forthcoming check before production completes (iirc - been a bit since I last futzed with production testing edge cases). If it's anything but an Item, you already have the physical entity available to makeover to someone/faction other than the one that is closing. I'd just re-assign manager & op to the new faction / someone active in there (you or otherwise).
If it's an ITEM type, it still shouldn't care about Operator/Manager for the existing "in-progress" production. However, there's a slight possibility when it spawns after production completes it'll have the Owner as the closed Faction (there's some bugs i vaguely recall concerning that sort of thing, which may or may not have been fixed). To be safe, I would do as you outlined (More particularly: Pause, re-assign, hop, re-start).