Here's why I don't think your reasons are valid and alternative solution to the username problem.

Your article explaining why you want to remove discriminators contradicts itself and is poorly thought out. It is clear to me that this article was meant to talk people in circles and hope people don't recognize the lack of substance in your explanation. Supporting factors listed below:

• Nearly every reason you give is either unrelated to discriminators (I cant find my friends username because they use uppercase letters) and/or actively made worse (Too many people want popular names, like "mike") by this change.

• You claim that you have considered other fixes and they ended up being half-measures, yet the only example you could give shares the same issue at an even larger scale (1/3rd of users have to change their names, yet this new system undoubtedly means that an even larger amount of people will have to change their name.)

• You keep repeating yourself. Difficulty finding names take up 4 of your 7 bullet points. I can only assume that this is because its your only legitimate talking point, and it seems clear that the writer was struggling to find others. One can only wonder why your company would want to push out an article of this quality.

• You preemptively moved to defend your decision as if you were aware that it was not a good solution. You try and tell us of the obvious solution to the case issue and why it wont work, while telling us that you're going to use that very same solution to solve the case issue, acting as if it is inherently intertwined with your decision to remove discriminators. 

If you want help people find their friends in discord, there are few solutions that should come together to make it as easy as possible.

1. Add a search function. instead of having to put in the exact name and discriminator to find someone, you enter a name and a list comes up including profile picture, username, discriminator, and other optional information such as an IRL first name, favorite games, account names for other platforms. You can also use location data (hidden to everyone but the user and Discord) to auto-filter friends that are physically closer to you, if each have opted in to give that data.
2. Remove case-sensitivity. You claim that almost 1/3rd of the users would have to change their name to accommodate this change. You fail to explain how this is worse than the much larger amount of people that would have to change their names who will have to change their name after the removal of the discriminators. It also isn't true, if you consider my next suggestion.
3. Add another digit to your discriminators, adding in 9000 extra people to a name. Now more people can use the name "Mike" and no one has to change their name to accommodate the removal of case sensitivity.
4. Link it to Steam, EA, Origin, ETC. This is so common these days, that frankly, its a no-brainer for an app like yours. Allow people to see which of their steam friends have a discord account that you haven't friended yet.

As far as I can think it through with what you've given us, this change is either lazy or malicious.

either you don't want to put in the work to implement the multiple fixes required to adequately address the issue, opting for one huge inefficient catch all solution instead

or

you think you can make more money selling premium names to nitro customers, but of course you cant tell us that, so you write nonsense to act as if this was a hard thought solution.