Has Fallen

Short Answer: Tokyo Has Fallen

The first one, Olympus Has Fallen, was about Washington, DC getting totaled. Then London Has Fallen was about... well, London getting attacked. Then Angel Has Fallen was back in, basically, DC. 

Time to go back overseas. Sure, we could have the series blow up the rest of Europe-- Paris, Rome, etc.

But Tokyo is a fun city to shoot in-- just ask the Fast & Furious crew-- and there are all sorts of scenarios for decimating it.

Just ask the Godzilla crew. 

Or you could blow up the Kremlin. No, not the colorful domes-- that's a cathedral. The Kremlin (which can also refer to the entire complex) looks more like what it is-- a government building.

And then skip Rio and go straight to Sydney. I don't think that's ever been blown up, or even shot up, on film, so it's their turn.

Cheech & Chong

Short Answer: Put all the stoner-buddy duos in the movie with them

The Cheech & Chong movies are not necessarily a franchise as such. I don't think there is a through-story, even to the slim degree of say the House Party franchise, with the same characters reappearing. But they made nine movies as a duo, and they were all similarly, shall we say, themed.

Also, Cheech is 76 and Chong is 84. So what's wrong with the idea of a last hurrah?

The story can be a simple quest. But in the course of, say, finding Pot-opia, they meet the other stoner buddy duos they inspired.

Namely: Harold & Kumar, Jay & Silent Bob,  Craig & Smokey (from the Friday movies), Dale & Saul (from Pineapple Express), Chester & Jesse (from Dude, Where's My Car?), ... and also maybe Wayne & Garth and Bill & Ted, whom I don't recall seeing doing pot... but come on.

The story can be structured along the lines of The Wizard of Oz, with new character pairs joining the heroes as they go. 

Along the way, they meet stoner icons: Willie Nelson (who is 89), Snoop Dogg, Woody Harrelson, Sarah Silverman, and others. These can be loosely based on Alice in Wonderland characters, as that story has long been assumed to have trippy inspirations. 

If Willie doesn't make it, then homage will still be paid. On the gates of Pot-opia will be, on one gate, his face, and on the other, Bob Marley's.

The soundtrack is going to be pretty epic as well. The above-mentioned musicians will be present, as will Cypress Hill and others. Don't forget, some of the above duos (and their characters) are musicians themselves. 

At which point... why not make the whole thing a musical?

But the focus will be on stoner-buddy duos. Scenes from other such movies can be watched by the characters, like Easy Rider, How High, Jackie Brown, and the lesser-known Leaves of Grass.

C&C will be able thank those who followed them to the screen for carrying the torch, and the younger ones will pay homage to the duo who... blazed the way (pun very much intended).