It would be nice to be able to have a "1-time only" subscription. This would allow for trial-type memberships that can only be purchased once per account. If this functionality is already available, I seem to have missed it.

It's not available, and would be a cool idea.

A similar suggestion brought up a while back was to allow users to purchase 1 or more subscriptions. I personally would prefer this one added.

I moved this, since it wasn't about IP.Content, and +1 for the ideas. Thank you.

Any movement on this feature?

We don't generally respond to most feedback with status updates I'm afraid. We just don't have enough time to respond to everything unfortunately.