@WalterT:
your suggested 4th line looks fun despite all overpayment on Lucic & Callahan
IMO the return for Lettieri & Vesey is just awful
and ... could you pls invest more $ into defense or advise who to improve the situation here?

My hope on defense is that last years first round picks, K'Andre Miller and Nils Lundqvist, will be a big part of the future. Miller plays the left, Lundqvist the right. They both had good D+1 seasons. I also like Rykov, who hopefully comes over from KHL to play next year. So, long term on the left we need three from Skjei, Miller, Hajek, and Rykov. On the right there is DeAngelo, Lundqvist, Gross, Andersson (prospect from Boston for Krieder). I'm pretty happy with the left side but feel a trade or free agent signing will be needed on the right. That can wait a year or two.
On the Lettieri return, he is Edmonton's reward for retaining 25% on Lucic, which could be a big deal the last two years of his deal. Without that they get Ryan Gropp instead.
On the Vesey return you could be right. I've been watching him for three years and have no idea what he's worth.