Is it ridiculous to think that maybe Hemalurgy is merely the process of ripping off a piece of spirit web with a spike, and that there is a grafting mechanic intrinsic to the cosmere which is what we are seeing used to add something to people with Hemalurgy spikes, soulstamps, and the new gemstone spikes?
I don't think what we are seeing with Moash is Hemalurgy because there is no indication that someone else's spiritweb is being used in these gemstone spikes. I think there must be something intrinsic to the cosmere where investiture can be grafted to bind points on a person to do specific things. If I am right, that would make it look like any investiture grafted to the eye sockets would give some sort of sight.
It is very interesting to see where this could go by capturing spren in the gemstones and grafting those to a person. Perhaps could a human with a gemstone in the chest get a form of power if the stone has the right spren?