Additional revenue could help the WvW game mode a lot, especially if those are usable only or mostly in WvW. Post your ideeas here.
These should be items & features that won't turn the game into P2W, and beyond being useful, are ways to show support for the WvW game mode.
Mine would be:
1. Gem Store based, WvW Gear Set Wardrobe: Weapon, Armor, Accessories, all existing current and future stats, including sigils and runes. This will be useful for those who don't already own an ascended set, this will be an equivalent - but usable only in WvW.
There could be multiple packs:
a. Permanent Unlock, for 50$ or so (equivalent in Gems)
b. Temporary version, for 50 Gem 1 day
Edit: or just multiple packs, and new stats included in separate upgrades: Base Pack (Vanilla GW2), HoT WvW Wardrobe Upgrade, PoF WvW Wardrobe Upgrade
Inventory Manager (not just WvW exclusive, but it's the worse when inventory full during WvW), an automated script that is executed with a single button click, that could do these:
a. delete items marked for deletion (minor sigils, other things you choose so when marking), useful when you are far from a vendor and inventory full
b. sell all marked items
c. eventually delete certain items as soon as they are looted
Cloaks and other skins