Keeping Username and Tag through a one-time paid use

When my subscription for plutonium ends I will lose my tag (it will be randomised).

Perhaps you add a one time payment where you can get to keep your tag forever (for that specific username and tag combination only after you have had plutonium for a month). Or, perhaps you can make a smaller subscription which contains the badge, the tag and the emojis (and excluding some of the bigger items like banners & streaming).