Tkachuk will work out just fine if Ottawa has moved to a plan of having a very large top scoring line, and Brown and Tkachuk add 15-20 pounds each and bulldoze. Unless you can really outskill your opponents, and that is very unlikely as a budget team, your top guys need force to score in tight-checking, which is almost all playoff games.
Tkachuk especially, and Brown for a 6 foot 6 guy have some finesse to go with the skill, and add a 2nd winger who can pound, and they could be basically a line of skilled power forwards. Add that to Duchene, Stone and Dzingel, and that is a nice top 6. Now just shore up the blue line, easier done if Karl stays, and you have something brewing.
Add Zadina to the top 6, and you have a mishmash with no real character, the kind that we haven't won the prize with in 25 years.