The brothers could be together

How do you pay Stutzle and DeBrincat next season?

Not even close to enough. Be prepared to be hurt with the prospects. Looking at losing a couple firsts and most likely a couple prospects or players.

Not for that offer.

Also think Tkachuk would ask for a 6-year deal to become UFA at the same time as his brother.

I think he'll be going on OS
Declining Arbitration leaves 2 options
Sign for 1x1 knowing your mimum avearge will be high enough
Sign a OS knowing you're leaving

Its not for a Trade
Usuaully they trade the players Pursuing Arbitration looking for a long term deal.
Tkachuk seems to be the opposite and a team would likely need to offer him like 8m x 2 years or something
CGY matches then Tkachuk got what he wanted walking into UFA status no more RFA/Arbitration/QO or OS nonsense.

Few teams are in the position to do that right now
Those that are i dont think he'd sign an OS for outside maybe STL
Most teams dont still have the picks required to get in on an OS deal TBH
Those that do dont have the Cap to make it work or the need for him

I think STL at that Term's interested as their team was build like 4 -5 years ago to win now
Their window is getting tight with each passing year and if Tkachuk helps put them over i could see giving up a late 1st for him in OS
That said i think CGY matches begrudgingly

Since the team elected arbitration, he's no longer eligible for an offer sheet. When the arbitration process is over, he'll have a 1-year deal with Calgary that they can either keep or trade.