Think u're overthinking it.
Strongest antagonists on Egghead atm are Kizaru and Lucci, so Oda's matching them up against Luffy & Zoro as you'd expect. Sanji going after Lucci would've taken this fight from Zoro. Moreover don't think the circumstances, are the same like I already stated earlier Stussy voluntarily took a hit that was directed at Vegapunk, Lucci didn't go after her directly so there's no need for Sanji to have specifically gone are Lucci for that. If it was Nami for instance, it'd be a different conversation. But yh even if you're not really buying my justification, you can just take it as the plot preventing Sanji from going after Lucci and giving us Smart Sanji instead of Angry Sanji in that scenario as that quick-wittedness is also very Sanji-esque. I see what you both are getting at with the Catarina ting but imo, doesn't really make sense for Catarina to have infiltrated that group. Not only is the huddle high with the likes of Jinbe and Robin still there, can't really see the price she could possibly be aiming for there. Moreover, this suggestion infers that Sanji has somehow been captured by the Blackbeard Pirates which imo is extremely unlikely. Rather than Sanji's group it'd make more sense for Catarina to have infiltrated Luffy's group. Bonney being down in the dumps doesn't only make an easy target but that group is also headed for the Sunny which has the Strawhats poneglyph rubbings so it'd make much more sense for her to be posing as Bonney imo.
Even if Stussy took the hit, wouldn’t you imagine Sanji to be pissed off at CP0? I’m not saying he should attack Lucci, but he should’ve showed a bit of rage. “Your partner left you out of the loop.” Is a cool line, but Sanji wouldn’t say something like that in this scenario where his partner stabbed and downed a woman. Sanji didn’t acknowledge Stussys sacrifice at all, and the idea that Sanji would for some reason think “It’s okay she went down cause she did it to herself.” Really doesn’t fit with sanjis character. And the “if it were Nami” idea doesn’t fit either. Sanji does not differentiate between women. He said it in Wano that he’s a lover of ALL women.
I think Catarina infiltrating the group that has the most to gain (the one by the Vegapunks) is the group she’d be in. Catarina came to Egghead before the straw hats or Marines were known to be here which means what they want related to something they already knew was on Egghead which means Vegapunk or the seraphim. Not the rubbings which they didn’t know were there.
And Sanji getting captured by a woman is a tale as old as time so it’s the easiest way for oda to implement this plot is by using Sanji. Robins still highly injured, and with the bubble gun now in their hands, there’s not really anything stopping this Sanji from trapping everyone.
As I said, the scene reads like a different person because Sanji was so calm after a woman got attacked which, even by accident usually sends Sanji off the rails, and then the convenience factor of now the strongest people in the room are gone and Sanjis holding a weapon that easily deactivates others makes this seem like it’s likely the BB pirates.