Given what we have to work with, I think the easiest way for them to fix the finale involves two minor changes, assuming we live in a universe where the production team learn the episode is going to be seen as an insult rather than a valentine, and/or they listen to Scott Bakula's criticism of the script.
1. Trim the episode and cut the CGI enterprise montage and end the episode at the "computer, end program" bit where Riker and Troi walk off. I would also say delete Trip's death scenes, but I don't think there is any other way to get to Archer walking out to give us speech with what they filmed without making really awkward cuts or filming additional scenes, which let's say for the moment isn't feasible. This is a "fix it in post" solution where the studio is telling us no to reshoots.
2. Change the episode air order - Have TATV air before the Demon/Terra Prime arc. This makes the episodes many fans feel should have been the final episodes the final episodes of the series that focuses on the Enterprise characters. Maybe they could also keep the CGI enterprise montage, and substitute a voice over where Archer starts off his speech, mentions something about the Gazelles, and then starts to tell everyone how the Federation wouldn't have been formed without the lessons learned from that fateful day on one of our earlier missions blah blah blah..." and then have it lead into Demons/Terra Prime. (Assuming the studio says no to reshoots, but begrudgingly say yes to some voice over work.)
This really doesn't address the fact they killed off Trip. But it re-contextualizes TATV to make it a fun one-off adventure, similar in-vein of In a Mirror, Darkly, which they had just done. Alternatively, combined with Demons/Terra Prime as a prelude, it makes it a little less bitter of a pill to swallow. You still could do post finale comics/novels/tie-ins that bring him back or say he didn't die/it was a clone / it was inaccurate.
At the end of the day, I think we just have to live with that unpopular decision, just like with what they did to Jadzia.