What about returns? Can you course them through JAC as well? Will Amazon then shoulder the charges or will you effectively have to pay again to send it back, have it replaced, and then shipped back again? Also, can you tell Amazon and JAC to group your shipments even if they come from Amazon Marketplace? Or does that apply only to items bought from Amazon mismo?
Returns? yes you can course them through JAC as well. But as per Amazon policy, they are only obliged to cover postage from NY/JAC Office(point of delivery) to their returns location in the US. In other words, when you need to return the item/s, you would have to shoulder all expenses should you choose to ship to/through JAC NY. for sensitive/delicate items, i prefer direct to Manila shipping so Amazon can replace this accordingly. Items like Schindler's List Gift Set/Disney Tins or Matrix Ultimate Collection should be delivered directly to Manila for easy replacements.
Yes, you can tell Amazon to group your shipments to few packages as possible, but no assurance. the need to check the items' availability in different fulfillment centers may opt Amazon to send each item from different locations. JAC, on the other hand, would treat each package as a different transaction and thus apply separate shipping and handling fee for each package. You may try dvdempire if you want your all of your items shipped at the same time.
As a rule, JAC does not group or consolidate packages into one shipping for security reasons and for the reason that this kind of service would entail tedious management/monitoring on their part.