Having the power to do this with Google's consent _and_ have it be available on mobile devices is huge.
I hope this solves the problem of conflicting Gmail extensions, I currently just have too many installed that don't place nice together.
[1]: https://gmail-message-id-finder.co/ [2]: https://www.inboxsdk.com/
We actually built the inboxsdk that you are referring to. There are a ton of extensions built using it and >10M end users using apps built with it. We've worked really hard to make sure apps built with the SDK are compatible. If you have any examples of 2 extensions not playing nice, def let me know.
Looking at it now, it's actually mostly InboxSDK extensions that are conflicting with Gmelius and some other custom extensions. Having 10+ extensions all trying to modify the DOM of one site at the same time is bound to give some problems :).
Curious to see if Streak will switch to this new official way, although it seems that a lot of the stuff you're doing won't be available to Add-ons.
As for Streak, we're planning on a mixed approach. The add-ons from Google support very few UI entry points (at least for now). Streak's entire UI only lives in Gmail so we need a lot more integrations. We'll use the Google sanctioned way when possible and fall back on the extension as we currently have now for the other cases.
We're having an issue with Gmelius interacting badly with our extension. Basically, we never enter our messageViewHandler code when Gmelius finds a tracker. Have reached out to them as well.