The thing is that you are then tying up a ton of cap up front and you still have the big needs at LHD.
We also have the unknown about how ZG looks with 15 & 23 down the stretch. He might actually be a better fit on that line than Nash would be.
Let's go on the hypothetical of acquiring Nash with ZERO salary return (just picks/prospects).
You move out franson for a mid round pick, leaves you with 5M to add a d-man. Assuming you are moving out one of Foligno or Girgensons to improve the D, that would give us plenty of space.
CapFriendly.com Armchair-GM User-Generated Roster
FORWARDS (13)
Rightwing: T. Ennis ($4,600,000) - S. Reinhart ($894,167) - B. Gionta ($4,250,000) - N. Deslauriers ($900,000)
Centre: R. O'Reilly ($7,500,000) - J. Eichel ($925,000) - J. Larsson ($1,750,000) - T. Schaller ($900,000)
Leftwing: E. Kane ($5,250,000) - R. Nash ($7,800,000) - Z. Girgensons ($2,750,000) - M. Foligno ($2,500,000) - M. Moulson ($5,000,000)
DEFENSE (5)
Right: R. Ristolainen ($6,000,000) - Z. Bogosian ($5,142,857) - M. Pysyk ($1,125,000)
Left: J. Gorges ($3,900,000) - J. McCabe ($1,250,000)
GOALTENDER (2)
R. Lehner ($2,225,000) - C. Johnson ($1,250,000)
BUYOUTS
C. Hodgson ($0) - C. Ehrhoff ($0) - V. Leino ($0)
DETAILS
Roster Size: 20
NHL Salary Cap: $73,000,000
LTIR: $1,500,000
Cap Hit: $67,953,691
Cap Space: $5,046,309