Ok so just looked at it on Cap friendly and with this lineup:
Drouin - Mack - Mikko
Nuke - RyJo - Kane
Lehky - Colton - Tatar
Wood - Oloffson - Cogs
LOC
Toews - Makar
Byram - Girard
Johnson - Manson
MacDermid
George
Prosvetov
We could have $2,525,000 in LTIR space to sign Kane. So I guess it is within the realm of possibility honestly. $2.5M seems fairly reasonable for Kane if he wants to win as suggested. The key being Francouz done for the year though, or at least if not done, traded away when he returned.
The depth here would be pretty nuts, but ultimately the teams success in the playoffs would still entirely hinge on RyJo and Colton at Center. I dont think Kane is that level of a difference maker anymore to where he could carry a 2nd line on his own.