CapFriendly shows us 68,532,501 committed to cap next year.
That includes Hertl, Couture, Labanc, Lindblom, Barabonov, Sturm, Lorentz, Kunin, Karlsson, Vlasic, Ferraro, Simek, Benning, Thrun, Knyzhov, MacDonald, Kahkonen, and Burns/Balcers/Jones.
Trade Karlsson while retaining 50% 68.5-5.75= 62,782,501 committed for next year with a roster of 8 forwards, 7 defenseman, and 1 goalie.
With the cap at 83.5, that leaves 20M. Zetterlund, Gregor, and Peterson will need new contracts if he wants them back and he needs to sign a goalie. That is going to leave a significant amount of room to take back some cap and do whatever upgrades he chooses.
Grier can absolutely trade Karlsson at 50% if thats what he wants to do.