Stuff I and others would pay money for in the store.

[JOTMON]

Player housing.
Start with things like Crew Quarters.. a small room with a spot for a chest.. Link into guild ship , or if unguilded.. a boat at the harbor.. or guidship entrance door..
Future opportunities to add.. bigger housing and more .... these are opportunities to sell space and many games have been very successful with player housing additions..

Add things like a Kobold butler(innkeeper) that makes various comments as he buys your junk loot and repairs.. "what Kobold supposed to do with this..", " you think you better than Kobold?", "oohh shiney Kobold keep this one", "kobold treasure this always"...
Many players would purchase a lot of housing options to upgrade to the Estate Castles and such...
Housing versions of guildship amenities...
and unlike Guildships no renown involved.. just purchases..

Succubus maid.
Game of Thrones Chair in front of a Dragon Head fireplace.
Multiple addable chests for storage
Hallway of Mannequins for displaying armor.. like dragon armor sets...
Monster Manual room.. ornamental room with various monster displays.
etc....

These are the kind of pay systems I would expect to see in any MMO games.
I am actually pretty surprised to see Turbine has not invested into this aspect of the game.