I'm not sure I understand all your model, but I'll try to answer your questions.
If the user is logged in, using the button will upgrade his account, if he's not logged in when he pays, it won't update his existing accout. So tell the user to login first in order to upgrade his existing account. If these new buttons are for existing members only, then just show them in a protected page so non-members don't see them.
Regarding Level 3 and 4 giving the same access, you could change the role of all Level 4 users to Leveel 3. This won't affect their subscription over at PayPal. You can go to the users list, filter to see only Level 4 users and change their role with the dropdown. Remember to make a backup before a change like this, just in case. WP Admin -> Users -> All
I see what you mean by changing the payments affecting the access, if they pay monthly they get Product A, but if they pay every quarterly or yearly, then they also get B.
If they're logged in to the account, using the Level 3 buttons, either quarter or yearly, should change their subscription and role. Buy a Level 2 account so you create the subcription at PayPal and then try the buttons to verify the role and subscription changes to make sure it works.
I hope it helps. 
Statistics: Posted by Cristián Lávaque — November 28th, 2011, 11:44 pm
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