The team could have made an agreement with Sekera to sign him at around a mil after the buyout.
So it was possible.
That’s considered cap circumvention which comes with a 7 figure fine and the loss of your first round draft pick.
You can only resign a player who you bought out if the player cannot find a contract anywhere else in the league. You cannot have any side deals like what you suggest.
Calgary is/was investigated by the league for what happened with Stone. But it appears Stone could not find another deal and so Calgary is/will be off the hook.
As well Sekera signed for $1.5M plus 500k in bonuses. Not sure how you have it locked in that Sekera would agree to a contract for half of his potential earnings here.