My list of things....
System Releated.
1) A Hybrid F2P system sort of like LOTRO, with classification differences. Subbies are still subbies with no account restrictions, Premium means you have subscribed to the service for at least 3 consecutive months, F2P is Free to Play.
2) Store Items are either Account Bound or Character bound depending on type of item and function.
3) F2P has no ability to gain scrolls from Spawns/T-maps. Nor can they use Non-Store purchased Scrolls. All scrolls can be purchased via store and will be character bound, if they are lost in combat they must be recovered by the buyer others cannot use them.
4) F2P Cannot place a house without purchasing the ability from the game store. This can be tiered. Minimal storage house is fairly cheap. Keeps and Castles not so much. Note this is just the ability to place these types of houses, not houses themselves.
5) Subbies/Premium get the ability to purchase the above in order to place 1 additional house and only if it's on a separate server. You could do Atlantic/Siege or Atlantic/Chessy your choice just not Atlantic/Atlantic for example.
6) F2P Can not get artifact drops at Peerless, Champ Spawns, or in Doom Nor can they use Faction Arties. This still leaves them ToT items like the RBC, Stromgrip, and paragon artifacts along with ML Minors and SA "Mini Spawn". All artifacts including Faction arties can be purchased via the game store. Game store Faction Arties will not be restricted to Faction players though. They will all be Character bound, if lost in combat they are worthless to anyone else.
7) F2P accounts are all inflicted with Siege NPC rules. Items cost 5x and NPC's will not buy from F2P players. Subbies/Premium players are not subject to this.
8) F2P/Premium players do not get Vet Rewards nor can they use them.
9) Subbies/Premium get +5 stat bonus and 720 skill points out the gate, F2P must purchase this. If you start a sub and stop payment before making the "Premium" time requirement you must choose which skill to loose 20 points in on next login if you would exceed the 720 skill point cap.
10) F2P doe not receive holiday gifts though they can buy them from other players.
11) Subbies can purchase Vet rewards from the store without account age restrictions. This turns Vet rewards from being a Status symbol in many cases into an actual gift for maintaining an account. It's a free store item
12) F2P/Premium can not access the Character Transfer System.
13) F2P has a 2mil gold cap Premium has a 10 mil gold cap per character. This will be enforced by making Gold a Virtual instead of a Physical item. Gold Coins used as Deco will stay in the game redeemable by handing to a banker to add to one's account, The same holds true for bank checks, in addition to this all monsters will continue to drop gold coins but just as a rarity similar to the Stout Whip on Orc Captains, Not uncommon but not common either. Checks can be draw for passing currency between characters. Characters going above their gold cap has this money put in a "Escrow" meaning the cap is in reality a spending limit more than a currency limit.
14) F2P can not Gain high Tier BoD rewards. For tailoring this means nothing above Spined Runics, for Smithing nothing above Bronze Ruics in rarity. The excluded items can be purchased via the game store.
Those are what I can think of off the top of my head... There are other things I'd like to see if I sat down and though about it
*** OK thought a bit ***
15) As Woodsman said, High Seas Boats can be added to the item store.
16) Expansions like SA and the High Seas booster can be made available via the Game store
17) Modified existing items.... Alcrity scrolls for example could be made in a tiered purchase system... 15 min. 30 min, 45 min, 1 hour, 1 day etc.
18) Exclusive Artifacts these can't be PoFed maybe say a 3rd Half apron that gives Stamina bonus similar to how the Crimmy effects HP and Tangle effect Mana. Or a Variation on the RBC that gives HP regen 3 HP Inc 10 and different resists totaling the same ammount. Higher in Physical and Energy for example..
19) One Shot Recipe Scrolls... meaning you learn it until you successfully make exactly 1 of the item. These scrolls could be used to make existing artifacts like the Spirit of the Totem or Armor of Fortune. The difference? If you use a special material you get it's bonus' added to the item, along with your Maker's mark for an exception item. For example a Barbed Leather Armor of Fortune would have 4/5/5/6/8 base resists along with the exceptional crafting/Armslore bonus' to resist if applicable. Spined would gain the 40 Luck for a total of 240 along with resist bonus'. Valorite Rune Beetle Carapace.... well you get the idea. Runic tools would have no effect on these items.
20) Gargoyle versions of current artifacts like the Spirit of the Totem, AoF etc. These are account bound. Add them as Drops at their respective peers location, Doom, Champs, Peerless etc for the Subbies without the account binding.
21) Make all of the Past Clean Up Britannia items available via the item store. Yes this would hurt the Rares market, maybe for some add a [replica] tag so originals keep a premium or some other identifier. Item Bless Deeds would carry a hefty cost like $20 - $25 each. These items are all Account bound, with the Item Bless Deed the item it's used on becomes Character Bound.
22) Crafting Tali's. A lot of folks want those max bonus tali's sell them..... Character Bound.
23) Library/Museum/Zoo rewards. Sell them, just make them all have a Durability and no ability to PoF and account bind them.
24) Add the Ability for Subscribers to sell gold to a Broker NPC in exchange for store credit. This would be the ultimate Gold Sink in a Hybrid F2P system. You are already collecting between $10 and $13.99 a month from subscribers, they are the only one's without a Gold Cap, they are the only one's able to acquire enough usable gold to purchase higher end Store items.