"Create Tage Subscription" improvement needed

in user/x/notifications/add/taxonomy, Create Tag Subscription

1) Autocomplete widget might not be the right one
Personnally I don't like it as you have to know first what you look for.
Give the option for a list / toggle / radio button...

2) Allow multiple select (already mentionned in other posts)

3) Multiple vocabularies are not correctly handled
In fact, Notifications is not usable with several vocabularies
All terms are flattens and mixed up without any refefrence to the corresponding vocabularies.
The form should display one selection widget per vocabulary, heded by the name of this vocabulary

Thanks for considering these important usability improvements.