As for my thoughts on Tali-I like to make peace honestly, but if not, I'm going to choose the Geth over the Quarians, who initiated the whole war,
That depends on your point of view. During the Morning War, the Geth seemed to have a massive advantage, ending it within a single year, and literally exterminated over 99 percent of the entire Quarian Species ("Less than 1% of the entire population" - According to Mass Effect Revelations), the vast majority of which I
highly doubt were combatants. Never once trying for a truce, never once trying to negotiate (if they did, Legion wouldn't hesitate to mention that, as it would help his cause), even though they had the advantage throughout.
These aren't exactly the actions of someone that can claim moral high ground, because defeating an enemy and making them submit is one thing, literally stopping
just short of making them completely extinct, and driving them off multiple planets under a year, is a
whole other level. That's something many of the "Oh, these poor, poor Geth" people seem to ignore.
Tali herself along with the Quarian Admiralty struck me as seemingly indifferent to the ongoing galactic apocalypse, choosing to pursue their reconquista instead-which just infuriated me playing through ME3.
I think it's the exact opposite. They knew the end was coming, and since they had nothing to lose anyway they might as well try to get their homeworld back.
Also, apparently they were already preparing for the reconquest of Rannoch shortly before the Reapers were made public knowledge, with them not giving up once the Reapers came because they were already committed, pressing on because if they lose they are all gonna be dead anyway, but if they win against one option they at least got their homeworld back (which, if you paid any attention, you know is a
big fucking deal for them, invoking it in their greetings, as an expletive, and so forth).
Would it be too upsetting to Tali fans? (Given if you choose the Quarians, you execute Legion at point blank range shooting him three times). Why does Tali not intervene or try to get revenge, when Legion and Wrex-both characters you can also betray take conscious action against Shepard.
I think you are putting too much blame on the Tali Fans here, though you are on the right track, as she is one of the most popular Squadmates which likely made such an execution unattractive from a writing standpoint.
Like, imagine if there had been a Mission in ME3 that forces you to choose between Ka'hairal Balak and Garrus, because of a war between the Batarians and Turians, and the Renegade option makes you blow Garrus' head off because he protests your choice. That would cause quite the ruckus among the fans. Tali is in a similar place, since she was around since the original game.
Legion? Well, he's a cold, calculating machine. He literally isn't capable of suffering the same shock as Tali would, so Shepard's refusal would make them his enemy. And since he's a Geth that just demonstrated his strength, shooting him three times would have been to ensure he doesn't get back up.
And Wrex? He attacks Shepard a good while after Tuchanka. He didn't come for Shepard immediately.
And Revenge? How exactly? She was shocked by Shepard's betrayal, likely paralyzing her. And there is no way for her to do as Wrex did, because the Normandy is the only organic ship leaving that planet.
If I had done the scene, I'd have had Tali try to intervene halfway through the upload, Shepard dodges her, and either drives the knife back into her chest, or somersaults around-pump her full of bullets and tosses her off.
That would be a superior scene. At least to me.
I think Shepard going John Wick on Tali wouldn't really fit the scene. It's supposed to be tragic, with you being forced to pick sides rather than mend the divide, not an action flick where you wordlessly blow the head off someone that's just desperate and, if dialogue, even as a Renegade, is any indication considers Shepard a friend, and just shrug it off. That would just be too over the top.
The three shots to Legion's head, even if he had just attacked Shepard, were a bit much too in my opinion, and doesn't really fit the tone.