I think it only makes sense for Vivaldi to integrate a few of the mods I use, things like the Sessions Panel the panel controls like zoom, kill, find, etc., and *maybe* Autosave Sessions.
More to the point though, the very existence of these mods makes all of them extremely low priority. I'd much rather have the Vivaldi dev team spend their limited resources on developing functionality I don't have access to rather than refactoring code to internalize it.
The effort to install & maintain mods is minimal. Directing new users to useful mods helps to illuminate the power Vivaldi provides the end user and grow the modding community. So while there are a handful of mods that make sense from a design standpoint to be internalized, I don't think internalizing them makes sense from a project management standpoint, at least at this time.
The ones that I think would make the most sense not only need to fit from a design standpoint, but would also benefit from ownership by Vivaldi -- that is to say they would grow beyond their current scope.
With that in mind, the Sessions Panel makes the most sense to me. There is some functionality that I think should be added to the panel, which wild be more easily done internally, and it is a superior UX to accessing and managing sessions than the current UI offers. In that case, both Vivaldi and the mod are benefitting.
Although it may not check all my other requirements, because it protects users from data loss I've included Autosave Sessions on the list. Unfortunately it typically requires a user being bit once before they investigate a way to have their session protected. The Autosave Sessions mod is great for that, and having it internal would really serve to differentiate Vivaldi as well.
But as a general rule, it's the functionality that people want which has not, and especially cannot, be had by installing a mod that I would rather have Vivaldi working to build rather than moving mods to the Vivaldi maintained code base.
