I think that if she does make music with Stuart and Max Martin she can deliver another amazing just pure pop album, Weeknd can be a mixed bag because his current singles are kinda meh.
I would like her to work with Blessed Madonna again for one or two songs, she did an amazing work with the Levitating remix and the current Kylie single produced by her is great too (it feels like Kylie’s BIM moment).
Also the Guess remix of Charli and Billie sounds cool and is produced by The Dare who has been mentioned lately as an upcoming dance pop producer.
And also James Ford who produced What’s Your Pleasure? for Jessie Ware, the music is lush, sexy, modern and that would fit M.
I hope that she sticks to London or European producers, Rebel Heart is cute but sounds dated and American producers suck at doing pop besides Jack Antonoff (Sabrina, Taylor, Lana); she should ditch Mike Dean too and the whole urban/rapper scene chasing she has been doing since RH, enough with the rapper features and bring some nice collaborations.