I think some WarioWare character could fit in a Wario Land game as side characters. Like for example having Mona giving Wario tips since it's said she goes on treasure hunt with him.
I believe they can easily share more elements with each other at least.
Like a WL game that contains microgames inbetween worlds as interludes. We'd have a mini WarioWare within the game and typical modes you'd expect in the postgame. But...
Found on the Super Smash Bros Ultimate subreddit. with a mix of Wario Land and WarioWare moves, a Wario Land stage, a mix of songs from both series and more characters from each:
I'd personally be okay with it.
This time you'll actually get to use the movement options in proper levels. You see the challenge levels (the WL4 inspired ones) feature two rankings, one for exploration/coins and the other purely for speedrunning/time