I think folks sometimes over-complicate this debate.
The challenge Kelmo sets out seems to me to be fourfold:
1. How do we retain all the existing subscription revenue
2. How do we gain extra players
3. How do we gain extra revenue
4. How does it make life more fun for existing players
The answer to 1 is really trivial. Someone has already commented on this thread that the shards are proof positive that folks are willing to pay monthly fees to own and keep a house, even if they don't play regularly. Many players pay for multiple accounts to maintain multiple houses on the same or different shards. So... in the F2P world you can't own a house unless you pay a monthly subscription (or maybe a lifetime subscription as they have in, for example, Star Trek Online or Neverwinter Online!).
The answer to 2 seems pretty simple as well. Allow F2P players to do everything except own a house. No skill total limits, no mining limits, nothing; just you can't own a house. Anyone, everyone, who gets addicted to UO ends up wanting a house. The current 14 day limit on trial accounts is not long enough to get people addicted. The current limitations on trial characters are a turn-off. You need a decent period of time, e.g. 6 months, to become truly addicted to UO.
The answer to 3 also seems pretty simple. The best F2P models avoid "pay to win" because that generates jealousy; what they offer is "pay or time" where you can pay to receive benefits that you could also achieve in-game if you committed sufficient time and effort; you could classify this as paying for being impatient, but that's really not fair. A fairer comparison is this; if you were unemployed you could stay at home all day, play the game and acquire everything through hard labour; but if you are working 10 hours a day in a well paid job, you can't play the game as much but you can use your substantial income to purchase things that you don't have time to play the game to acquire. So either way, the rich and the poor end up with the same loot, just one invests time and the other invests cash. Trivial example; sell 120 skill and +25 stat PowerScrolls for cash.
There's an extra level of sophistication you can build into this "pay for time" model that generates money for both the gaming company and the "time-rich/cash-poor" players. In Star Trek Online, for example, there's various stuff from Cryptic that you can only buy for Dilithium, which comes from mining but each character has a cap of mining 8,000 per day. It takes time to mine 8,000; the "time-poor/cash-rich" players can't invest sufficient time. But they can buy Zen from Cryptic, at $50 for 5,000 Zen, and then use the Zen to buy Dilithium off the other players via the Dilithium Exchange. Poor players can therefore invest time mining, just as scripters do in UO, and sell their Dilithium to rich players thereby earning Zen, which is used for the best ships and stuff in the Cryptic store so in our terms say PowerScrolls and all the products in the Origin store.
The answer to 4 comes from the above. For example, existing players can get access to stuff they currently pancake about not finding easily, e.g. PowersSrolls for money, probably no different to the way they use the sites that shall not be named today, but the money is being recycled into Broadsword/EA instead of China Inc. Another example, there would be more F2P players around in game looking for high-end gear from vendors run by existing subscribers since only subscribers would have houses to place vendors in. Another example, there'd be more activity on the shards as the F2P players would be populating places that maybe a little dead right now. More players = more community = more opportunity for interaction.
Very little of the above even takes much programming. The trial accounts already have the no-housing limitation. The introduction of the vendor search already gives us a shared marketplace for subscribers to sell to F2P players. The introduction of a currency to simulate Zen and Dilithium is something to develop, but we already have Silver which is now unused since Factions were killed, and maybe we just steal another consumable (e.g. Power Crystals because they happen to look just like Dilithium!), and the work on the Origin store so Silver can be used to pay for stuff instead of dollars.
Call me mad, I'm sure you all will, but to me it really isn't that complicated. F2P would be a fail if housing was free, but really, no-one's that silly I hope.
