If the Raptors are out of it, and are looking to rebuild at mid-season, and if Lowry has asked to move on to a contender the Nuggets should strongly consider going after Kyle Lowry who is signed for 2020 and 2021.
They have a few options to match salaries while still helping their current roster:
1) Millsap + assets
2) Mitchell Plumlee + Will Barton + assets
That allows Murray to play more off the ball, and you have a much more reliable point guard and elite defender. Lowry's value in the last 2 rounds of the playoffs, and his regular season value, has always been understated.
Or as crazy as it sounds Lowry + for Jamal Murray. Murray is a big contract, and is he the player that can win championships. With Lowry you are much more likely to contend in 2020 and 2021, and you have guys like Harris, Beasley, Millsap, Morris that can benefit from 2 of the smartest players in the league in Lowry and Jokic.
Preferably, I hope that the Raps have a handshake agreement with Lowry for a bargain contract in 2022, after giving him the healthy one year extension. That then leaves the Raps with quite a max salary cap spot to add to Siakam.