Yes, if we bring in two more forwards and the end result is Dever being bumped down to the 4th line with Whitehead and Yanni I certainly wouldn't complain. That line would be very quick (though undersized), and would be a strong puck pursuit line. Perhaps that's where Horner comes in to add some muscle to that line as needed. I've been impressed with Yanni so far, he has the makings of a really good forechecker.
The priority now should be the centre (and the backup goalie to replace Donoso if he is in fact let go). I'd like more size and physicality up front, so perhaps that is what the winger addition can bring.
Smyth often loses his man in coverage in the defensive zone or gets caught looking the wrong way or picking up the wrong man. A couple of the rebound goals by NB/Kingston players over the weekend where Smyth/Ewles didn't tie up their man in front. He can win puck battles and is a reasonably good skater and puck mover for a big guy, but I question his defensive awareness. Sirman is better in that regard and can help offset some of Smyth's shortcomings, but they aren't the conservative, lock-down 3rd pairing I'd like the 67s to have.
Like you said though, its a matter of priorities. I agree with what you laid out.