Thanks for enlightening me. So for the (1) case, it's a challenge for me on how to educate the vendors setting up their shipping options through the vendor dashboard. Because some of them have posted discounted bulk/wholesale items (clothing products) let's say 3-10 pcs so obviously the shipping fee will be higher compare to retail order since the parcel will be bigger and heavier. And also, the interface or options in vendor Shipping setting page is a bit confusing actually.
So I am planning to set a global flat rate shipping class (for bulk and retail) and will be added on each vendor orders (if customer bought at the same time from multiple vendor). So now I am thinking to consider the (2) case, planning to tie up with some courier company and then for every order, the courier will pick up the parcel from the vendor and deliver to the customer. The fees will be paid by admin but will be included and paid by the customer upon checkout.
What can you suggest or advise on my situation? The site just launched recently so this is the drawback I can see that's why some newly registered vendors didn't proceed on posting their products. Even, posting new product is a bit complicated if I am a layman.