So at Quakecon 2018 the developers discussed adding new features to ESO Plus to make it more rewarding and I thought it would be a great idea to post some of the ideas I had, maybe get some traction and catch the eye of one of said developers.
#1: ESO Furnishing Bag (as suggested by antoniotf5
https://forums.elderscrollsonline.com/en/discussion/435267/eso-plus-furniture-inventory ) This would be another bag, much like the crafting bag which holds an infinite number of furnishings in one place so they aren't eating up bank+inventory spaces. for those like myself who have half a million books from lore furnishing sets to fill a library this would be a huge boon so i didn't have 50+ book furnishing i have that can't be stowed anywhere on account of no space.
#2: Rewarding active subscribers would also be a big step towards making ESO Plus more worthwhile. While we do get a small allowance of crowns and access to DLC, I believe that offering rewards to those who buy consecutive membership month after month would also go a long ways towards encouraging more subscribers. An example of a reward could be giving out a handful of crown crates each month (with the number going up slowly with every month they keep an active subscription), or perhaps offering a small bounty of crown gems so they could buy something they want from the crown crates.
#3: Bolster the already existing perks of ESO Plus. If you wanted to make ESO Plus worth more than a means to have an infinite space for crafting materials, bolstering the exp boost, gold find and further reducing crafting timers would also go a long way. It used to be that we had glyphs that let us bolster the amount of gold we received from kills which has long since been removed and replaced. While what we have is okay, it is still nowhere near the bonus we had from enchanting our gear with that effect.
#4: Adding more perks that affect the player throughout their subscription time. We already have small benefits like i mentioned before (exp boost, more gold, shorter researching timers), but why not add to that, such as boosting the AP players get from Battlegrounds and Cryodiil, increasing the number of keys we get from daily undaunted pledges, or offering a free item from the crown store that changes every month. (like offering a pet one month, and a costume the next, etc)