Regarding HTML: one way to see it is that HAML should be used. As suggested in the discussion that you referenced and as I wrote on GH. By requiring translation, you cross the line from simple static usecase where HTML is enough and get to the point where you need to call functions or do branching. And we use HAML for that.
I prefer to limit the number of ways to do a single thing in a single project. But we can surely discuss the possibilities. Especially in the context of the self-service and other new UIs.
There’s e.g. this: https://angular-gettext.rocketeer.be which seems to be compatible with the tools and processes that we already have in the mix.
But theres work involved with use of such tool such as packaging the necessary dependencies and making string extraction work. We should consider what we get for the effort.
Should the result of this effort be that we can allow use of HTML in places where HAML would be used otherwise, then I am not a fan of that.
But if the result would be that we have a unified way to do i18n for self-server UI and for other possible UI’s on top of ManageIQ then it might be worth serious consideration.