abcsupport - Thanks for posting your question on the forum!
Unfortunately, at the time of this post, there is no way for AOS devices to load balance based on bandwidth. As you probably read in the AOS load sharing guide, Configuring IP Load Sharing in AOS - Quick Configuration Guide, load-sharing is done based on connections as opposed to bandwidth. Specifically, it can load share based on a per-packet basis or per-destination/per-session basis.
Please do not hesitate to let us know if you have any further questions.
I went ahead and flagged the "Correct Answer" on this post to make it more visible and help other members of the community find solutions more easily. If you don't feel like the answer I marked was correct, feel free to come back to this post to unmark it and select another in its place with the applicable buttons. If you have any additional information on this that others may benefit from, please come back to this post to provide an update. If you still need assistance, we would be more than happy to continue working with you on this - just let us know in a reply.