Lack of interest Account upgrades - allow next level to discount previously purchased upgrade

Requesting two features for Account upgrades:

  1. If a user wants to purchase a permanent account upgrade, there should be an option to discount the current upgrade a user has already purchased. For example, if I have the options of a $10, $25, and $50 account upgrade, if the user has already purchased the $25 upgrade, then to purchase the $50 account upgrade should only cost $25 since they already paid $25. This should be an on/off feature.
  2. Terms of Service/Conditions/or Agreement option should be created so that we can create a custom TOS just before the user logs into paypal. We need this legally to protect ourselves.
In the mean time, are there any plugins/addons that do this?