I had some ideas I thought I would post to get feedback on.
1. The farming of motifs: We all know there is an issue with the farming of motifs and the drop rates. The solution I propose here is to remove Motifs from normal containers and to place them in lockboxes (give them a drop chance). The higher level zones and locations have a lower chance to contain the rare motifs.
2. Currently there is no real point in progressing a crafting skill past level 40 as at that point you can put the last skill points into the craft. Granted there will probably be some reason to progress as more content gets added.
What I propose here is to modify the crafting system so that higher level crafting skills reduce the amount of base materials needed to craft something. I.E. a Master craftsman makes less mistakes and therefore is more efficient on materials.
3. Currently there is the so called Guild Tax on sales done in the guild store. Place this gold into a limited use account. This account would only be used for leasing/renting a public store in a locked system. What I mean by a locked system is that no one could actually access these funds. They would be accessed by the system when a guild tries to rent or lease a public store.
4. Zenimax wrote something a while back regarding their vision for guild stores. They envisioned that guild would start to specialize in what they sold. Currently when I look into guild stores most of what I see are dropped items as currently the dropped items are simply better than crafted items for the most part. Aside from dropped items I see materials for crafting. As long as a guild leader cannot place rules on what can and cannot be sold in the guild store there is very little chance of a guild specializing. The other major factor working against guild specialization is the inability to make a store public except when your guild controls a keep in Cyrodiil.
As a solution guild could rent/lease public stores for x amount of gold per x amount of weeks/months what have you. This could be funded using the "guild tax" on sales in the guild store. Once store are open to the public guild would be able to specialize. Allowing a guild leader to limit what type of items could be sold and/or what level of items could be sold in the guild store would also drive guild towards specialization.
For example it is getting harder and harder to find lower level dropped set items. A guild could specialize in selling these types of items.
5. Membership Fees: Another change I personally would like to see is the ability for a guild to set a membership fee that would be deducted from the members on a weekly or monthly basis. These funds could be used to purchase material for the guild, buy bank space, PVP gear such as trebuchets, repair items, soul gems etc. If members of the guild did not want to pay the tax then they could leave the guild. Again this would cause guild to specialize more as like minded players would eventually start to connect.
6. Guild alliances: This is another subject that would lead guilds to specialize and connect with each other. If guilds could create a meta guild alliance consisting of X number of guilds and being in a Meta guild alliance would permit players to use the stores of other alliance members depending on the settings of the guild store.
[TL:DR] Just some ideas to to improve/add some functionality.
Move motifs into lockboxes.
Reduce the amount of materials required to make something based upon crafting skill level.
Allow Guild leaders to place level limits on items that can be posted in guild stores.
Allow Guilds to lease/rent stores open to the general population using sales tax
Guild Membership fees
Guild Alliances
Cross alliance shopping
Store rules for alliance members