In all honesty I don't know much about Dobson except what I read about him& it reads like he could also be a very good defender, however, I have seen Boucher ranked higher on almost every poll I believe. I have seen Bouchard a few times now & he is a solid defender who quaterbacks the London PP & IMO looks to me to be a very good two way defenceman. If Chabot turns into the dynamic offensive defenceman we all think he can be than Bouchard would be an excellent partner for him in that he is big & strong defensively, can skate well & also brings some offensive ability. IMO they would make a dynamic tandem. He is different than Ceci in that I expect him to be better defensively & have a higher IQ offensively which is why I like him with Chabot, a guy who can read plays at high speed better. I like Ceci on the second pairing but he could use a partner like Bouchard on the left side.
Another guy I like but don't know as much about except what I read about him is Bode Wilde who is also a RD, big & strong & supposedly very good at both ends of the ice. I have seen Wilde on some polls ranked in the top 10 as well as higher. He would be a good replacement if we don't get Boucher or Dobson later with their 2nd 1st rd pick by trading up. I agree with your assessment & we may very well see a number of changes to the ranking during the draft, we always do & a couple of guys could sneak up into the top 10. Wahlstrom looks like a guy who could easily sneak into the top 5, very skilled player. IMO it would be a terrible idea not to keep this yr's draft pick on a hope of drafting higher next yr, it's a risk or bet that could too easily backfire. Pick a good player now while you can.
On Tkachuck, I just think him being a very good American player who played for the WJC American team with such a high profile makes sense to me anyway that if Buffalo does not win the lottery that they would take him next to help sell tickets. Regardless, IMO Ottawa need to keep this yr's pick because there are a number of players who could turn into very good players for Ottawa, if not dynamic players they could certainly fill some needs. They have a full yr afterwards to worry about the 2019 draft & lots could happen until then including some trades which could garner them a 2019 1st rd pick or two.