Hi InfoUser,
From the description, I see "I have a portal through which I resell different vendor's software licenses". Does it mean that you are a Partner of Office 365? If so, we offered a specific support channel for our partners. You may reach the support by following link to get better support.
Partner Communities: http://partnersupport.microsoft.com/
Partner Communities for Online Services: http://partnersupport.microsoft.com/en-us/mpnonline
As we can provide limited assistance to your requirement, I also suggest you post the question to the MSDN forum to see if they can find a workaround for you.
MSDN forum:
http://social.msdn.microsoft.com/Forums/en-US/categories
Thanks,
Aaron Yuan