Add a translucent version of a subscription icon for "Prior subs"
With prior subs being represented, viewers and broadcasters could see who of their current viewer count is a prior sub. This will help represent many things. Short from long term subs that let their sub lapse creates discussion, it also lets people know that this viewer might be a little more well versed in the channel content than someone brand new.... etc.
borrowing this idea for my compilation of ideas tied to sub lapses: https://twitch.uservoice.com/forums/297558-general/suggestions/33693295-respect-people-who-have-to-have-a-sub-lapse-indic
This would also be useful to add another layer for the business end of things, as well as the social aspect. It promotes re-subbing more than showing that the person was never a part of that community.