Yep, I did it. Took advantage of Monday Midtown Mayhem and started Cosmic Prestige on Hawkeye. Managed to get to Level 26 (running several XP boosts) in exactly 4 hours.
Finished Story Mode Chapter 1-3 following to this guide as usual (for the rewards, not everything) and the rest was spent in Midtown, always joining the bracket 2 levels too late and leaving it 2 levels too late in order to not fill up on reward chests I can’t open so much (i.e. joining the 15-19 bracket at 17, leaving at 22).
I don’t want to know how long it will take and if my 25h estimation from yesterday for the whole thing is too high or too low, but I’m gonna make it!