While monroe is weak defensively, it doesn't mean the knicks have to be. To be fair Charlotte had a top 5 defense with Al Jefferson at Center. Al Jefferson is just as much a liability on defense as Monroe in normal situations and even in this defense they we're weak to the pick and roll. However besides that Coach Clifford defensive scheme compensated for and hid Jefferson and PF's such as Marvin williams, Cody Zeller, and Josh McRoberts defensively for the most part.
http://www.foxsports.com/carolinas/story/charlotte-hornets-improving-defense-once-again-among-nba-s-best-020315
Basically they limit drives by crowding the paint and defending the weakside even if it leaves them open to outside shooters (sound familiar)
More than just the bigs goes for the rebounds and they do box their man out
They have an amazing defender in MKG who can defend man to man without fouling
They limit opponent transition points as much as possible
Here is a breakdown by the blazersedge blog on why the charlotte defense works.
http://www.blazersedge.com/2014/10/6/6897193/portland-trail-blazers-strengthening-weakside-defense-key-blazers-defensive-improvement
Keep in mind MKG (who is a 2016 RFA) is a big part of the Hornets top 5 defense, but the knicks don't need to be a top 5 defense next year. If they can make it to the top half that would be great. A bastardized version of what the Hornets are doing could work as a defensive scheme for the knicks. They will just need more defenders on the roster.