You'd have to do what we did. Bite the bullet, start shipping out the misfits, pensioners and pseudo big names, select 5–6 players from the first XI as the kernel of the new project, then spend 3–4 years recruiting, expecting you'll finish midtable for at least the first two of those, certainly you can rule out Champions League qualification, and expecting to spend a nett £500m.
Their first team's already so makeshift I don't reckon swapping out the plebs for semi-decent youngsters would hit their results too badly.
The money will be the issue for them but too bad, so sad. My guess is Ange has been told that the bankroll won't be there because they won't compete in the new Champions League. Given having pulled out just one additional win since Christmas would put them in with a good chance, he's fucked it.
It's a similar situation to Arteta two seasons ago, but it's a mite worse due to Postecoglou's lack of pragmatism and acumen. He's kept saying to the players "We're going to follow my plan even if we lose," so now he's got a group of players who see losing as a viable option every week. Arteta has never strayed into that sort of territory.
From where Spurs are at at the moment, shooting for a league title looks like a decade long ultra-patient project. Given they haven't won anything of note in over 60 years that should hardly bother them. Fuck 'em indeed.