The current token system is good, but it could be better. Here is my proposal, all numbers purely to illustrate the concept.
A new Generic WoW Token (GWT) sold instead of the current WoW Token, sold at a set price. Let’s assume it is sold for $5 in the Blizzard store for example.
Services for sale would include game time, but also every other automated electronic service. Game time, mounts, server transfers, name changes, character boosts, or even digital editions of expansions.
The services would be sold in token units. What I mean is, if 30 day game time token is valued at 4 GWT, and the current market price of a GWT is 5,340 gold, then the game time token would be listed as 21,360 gold (5,340 x 4 = 21,360). A $60 character boost would be 12 GWT, listed on the AH for 64,080 gold (5,340 x 12 = 64,080).
Players would not see the game tokens themselves listed for sale in the AH, players would never buy the tokens for gold. Instead players would buy whatever service struck their fancy, and buying that service would simply buy the correct number of GWTs currently listed, with the player paying in gold. This is similar to what we have now, but with multiple tokens being bought simultaneously for purchases worth more than 1 GWT.
This system prevents both the seller and purchaser from having to worry about market demand for any specific item, allowing all services to be made available.
Posting this here as a dry run and I forgot I disabled my ability to post on the official forums to focus during finals, gonna take a few hours to re-enable.