I don't really understand what you want.
You still have exactly the same options as before, except now more people will want to play with you (those that require their opponents to have cards).
If you don't want to play with anything except base cards yourself, then buying a subscription to non-base cards isn't going to help you, but it won't hurt you either.
The original poster is being harmed by having bought a subscription, because they can no longer play rated games using only cards from the base set. And by far
the fastest way to find a game is to use the automatch feature to find rated games.
One solution would be to refund all but the first month of the original poster's subscription, and remove the subscription. Another solution would be to allow a player to "deactivate" the cards that they have purchased, so that they can, for example, still play rated games as if they only had the base cards, but can mix in other cards when they want to. Similarly to this poster, Burning Skull had to create a separate account called "Drowning Skull" for his great "How to Base Dominion" series (https://www.youtube.com/watch?v=JpPtxyGNGcg
) because it is much harder to get a game with only the base dominion set if you are a subscriber.
More generally, the difficulty of transitioning to games with lots of new cards for people new to Dominion suggests that there should be a subscription option less expansive than Silver - say, an option that adds only Intrigue and Seaside- to ease this difficult transition (I created a separate thread to discuss this: http://forum.shuffleit.nl/index.php?topic=2185.0