the arab slave trade was very big in eastern-africa for more than 2 millennia, and cause untold suffering.
could it be plausible they start raiding eastwards also?
Well, it did existed : Western Indies and Dutch plantations used Indian slaves or half-slaves (indentured workers) up to the XIXth century.
Having it on a larger scale however, encounter some issues.
It's a bit too far from their productive cores to be really interesting on a much larger scale : Africa is just right there after all, and Indian Ocean slave trade was importantly under Arabo-Indian dominance.
with regards to the dutch there was the big issue of west-india company and the huge and influential VOC (dutch east-india company), the WIC was only allowed to trade in the americas and west-africa,and engaged in the standard slave trade (although it was only 10% of their actual trade). the VOC on the other hand had one or 2 experiments with slave plantations, but abandoned them. the slavery in the east-indies was more the domestic servant style slavery (like during roman times), plus was limited due to the VOC using all the roman laws with regards to protection of slaves plus some extra (slaves could only be sold on to christians, a slave from VOC territory setting foot in the netherlands would automatically become free etc), these laws pretty much restricted the trade.
And since the VOC was all about the money, i guess they figured extensive slavetrade wasn't worth the hassle.
the indian indentured workers were post WIC (19th century). and the majority only arrived in last 25 years of the 19th century, due to a contract with the british government. don't think this can be scaled up.