The game played in the guide can definitely be improved on. I managed to break 3 vulnerabilities to T1 and one to T2 on day 11 with the same chosen. I actually had to hold back to not break the minor vulnerability to T1 too.
Generally I think its not a great idea to be using evil energy on commanders just for extra angst. It doesn't seem worthwhile.
Edit: Replayed and managed to break all of Vertem's non-minor vulnerabilities to T1 on day 9. Going to write my own guide when I have time.
I agree with your assessment to a degree, but one thing I do want to say though is my guide is built for beginners in mind mostly. A lot of people have had trouble with understanding the game, specifically the flow through the days, understanding the mechanics and how they are interconnected with each other, and most importantly; planning out the form of attack and the target in advance.
As a result, I intentionally kept some of the objectives and the battles simple. If I don't and I try to explain too much at once then people will be too confused to digest it all, (which already happened to a degree lol) and if I try some of the more complex strategies I use in my normal play then players will get too intimidated when they're having trouble just breaking a core vulnerability or getting decent EE in later stages.
An example of this is in second day where I mentioned psychic reading and its important utility when you're learning how to play, in my normal play, psychic reading is the upgrade I pick last in the early game because I can tell some of the core and minor vulnerabilities from the their first entrance and even more later with their bio at the end of their first battle.
I didn't want to save scum often in that run to keep the flow consistent and simple and encourage players following along to experiment and grow used to planning out their actions.
With all that being said, I'm looking forward to the guide you make, breaking all of Vertem's vulnerabilities that early is impressive and I'm looking forward to seeing the strategy you employed!