Guardians/Avengers is happening. Likely Avengers 3. When it comes to expense... you think they can't afford it? You think it's not going to recoup four times over? Jeez.
They can just do it like they do in the comics.
Have GOTG fight Thanos in space, fail, Quill or someone lands on Earth to warn them. Thanos comes to Earth. He's the villain of Avengers 3, but sends his forces to AOS/Daredevil/Luke Cage/Iron Fist/Jessica Jones/Defenders TV shows. So there's a threat across the Marvel spectrum.
Heck, maybe if they do an Agent Carter S2 you can have a warning of Thanos invading be the reason Hydra infiltrates Shield/Shield starts prepping Phase 1/Howard tries creating the new element etc.
I mean Shield has that Infinity Stone for a LONG time.
And then you can launch Black Panther after Avengers 3 (Wakanda was attacked, blames America for being greedy) and Captain Marvel (powered by Infinity Stone explosion or some shit) as 'A3: Epilogue.)
Marvel comics events take in everything, eventually the films will too.