Well yeah the most intriguing thing about adding Machado now would be winning now. You immediately upgrade your weakest offensive spot. Would still be a lot of question marks but if you got him, you would indeed want to sign one of the top four starting pitcher free agents now, and probably a higher-end reliever too.
But getting him for only the money - which you'd have to pay anyway - is better.
Frazier is probably more interesting to me than Moustakas if they wanted to be that aggressive about abandoning Franco, 'cause he could always be traded or eased into a bench role (he's also willing to play 1B) in 2019 and 2020, and you can probably get him for just three years. Moustakas in 2020 might not be pretty, as andy notes, and he'd be signed through 2022. I doubt they want that.