Its not flawed. Its more than likely their best case scenario.
The other 2 scenarios are, 1. drop in cap (say 5mil) and a cbo. That would still leave them 26.5mil to 29.5mil free cap. Or 2. A flat cap with no cbo. Here they have to hang onto Eriksson, leaving them 25.5mil to 28.5mil cap if they make the same moves.
Why are these moves doable? Because the Canucks are at a point where they have too many players/prospects competing for a small number of spots. Look at the #6 and #7 D spots. You realistically have Benn, Stecher, Tryamkin, Rafferty, and say 1 more prospect (Rathbone) competing. Benn is tradeable with a 5th or 6th attached to him. 1 of Stecher/Tryamkin can be included with someone like Baertchi or Sutter to create a better return/ reduce loss of prospects/picks in the deal.
No, it is flawed. If the cap stays flat and there are no CBOs, they keep their current 18m cap room. In your scenario you buyout Eriksson to help "create" another 13.5m in cap space which is pointless. If there was a CBO the cap would drop, maybe by 4-5m or whatever, hence instead of the additional 13.5m it would be rather 8.5-9.5m cap room.
Now for your whole spin of having 25+m cap space, you probably should also take into account that with that, the team is lacking almost half a roster. So lets say they can trade Sutter ($1m retained) and Benn and Baertschi (all three of them will cost assets to get rid of). That gives you $25.67 space and you need to sign at least 3 F, 3 D and 1 G just to have the minimum 20 player roster. Who is going to be #4 and #5 D for you? Right now you only got Myers, Edler and Hughes while 5 players competing for 6/7, so you need to sign Tanev (or comparable) which costs 5.5+m. You also need to sign Markstrom (another 5.5m deal at least) and Virtanen.
Just to make it visible, below a quick armchair GM team from capfriendly
CapFriendly.com Armchair-GM User-Generated Roster
FORWARDS (13)
Right wing: Brock Boeser ($5,875,000) - Tyler Toffoli ($5,500,000) - Jake Virtanen ($3,000,000) - Tyler Motte ($1,000,000) - Loui Eriksson ($6,000,000)
Centre: Elias Pettersson ($925,000) - Bo Horvat ($5,500,000) - Jay Beagle ($3,000,000) - Adam Gaudette ($1,200,000)
Left wing: J.T. Miller ($5,250,000) - Tanner Pearson ($3,750,000) - Micheal Ferland ($3,500,000) - Antoine Roussel ($3,000,000)
DEFENSE (7)
Right: Christopher Tanev ($5,500,000) - Tyler Myers ($6,000,000) - Troy Stecher ($2,325,000) - Brogan Rafferty ($700,000)
Left: Quinn Hughes ($916,667) - Alexander Edler ($6,000,000) - Jack Rathbone ($925,000)
GOALTENDER (2)
Jacob Markström ($5,500,000) - Thatcher Demko ($1,050,000)
BUYOUTS (1)
Ryan Spooner ($1,033,333)
RETAINED SALARY TRANSACTIONS (1)
Sven Baertschi ($1,000,000)
DETAILS
Roster Size: 22
Salary Cap: $81,500,000
Cap Hit: $81,483,206
Cap Space: $16,794
Now this does not include the 1.7m bonus carry over for Hughes and Pettersson, the the team above is already above the cap and only workable with LTIR of Ferland (who btw is currently expected to play in fall. To pretend they have loads of cap space is pretty laughable considering they can barely keep the team together and stay under the cap, all that while trading away more futures just to get rid of Sutter, Benn and Baertschi.