None of those moves individually or all together make near the impact Correa made last year. It also leaves like $20M on the table from last year's payroll. Hell, you could probably do most of that AND sign Correa and not be far from last year's payroll. And remember, the question was "how do they spend the money?"
The "internal options" at SS are all question marks at best.
I wouldn't consider Farmer a "stable veteran" as much as a utility man who can play SS if needed.
You're worried about Correa's metal plate? What about Lewis' ACL that's been torn twice? Does that make you think he's a sure thing to play SS in the MLB? I'd need to see more once he comes back before assuming he's the SS of the future.
Lee has spent half a year playing professionally and I doubt if even the Twins have a good idea if he can play SS at a Major League level.
Correa plays SS at an elite level and has been consistently elite throughout his major league career. Not only do you know what you're getting with him, unlike the options laid out above, but you're getting at worst a top 5 SS. Likely for the first half of a 10 year contract anyway.
Your idea is certainly a possibility, and probably all of it's more likely than Correa returning to the Twins, but does any of that add wins let alone replace Correa's 4 WAR from last season? Not even close.
Correa is basically the only way they can add wins without trading away player capital at this point.