I don't think a winger upgrade can paper over the lack of a Ceci replacement, unless that player is a possession monster (flirting with 60% CF%), if push comes to shove we might have to try and change the nature of the pairing. Like the Nurse- Ceci pairing has gone into a lot of tough defensive match-ups in the playoffs and keeps coming out on the losing end, for example I would consider Colin Miller a modest downgrade on Ceci, but if we ran a Nurse - Miller pairing the transition game would likely improve and we'd likely be on the attack more often, even if the actual defending might be even worse, we would be better equipped to hide from that weakness rather than play into it.
In terms of our prior playoff losses I think you learned the wrong lessons from them. The Colorado series was lost entirely by the gap in quality between their D and our D, they were also absolute beasts on transition that we could not hope to match, our ability transition from offense to defense and defense to offense was nowhere close to them. With the VGK loss that was primarily a goalie gap, but they also laid a whooping on us 5 v 5 mostly from the Eichel line beating on every line (though McLeod did alright into the match-up), it also highlighted our buy-in to a team defensive game didn't match their buy-in and they exploited holes in our man-to-man defensive structure.