I am slightly curious as to why a vaasalich would be hard to make and I think we might be overthinking things a bit. I think all it would require would be some fiddling with the scripts for vampires to make the coffin a phylactery instead with the appropriate placable. There would be no forms available for the vaasalich, but when you die, you turn into a form similar to the mist form (different appearance maybe?) so that you can return to your phylactery. From there, all you'd need to do is change around the creature item to be more fitting for a pseudolich. As far as abilities, perhaps a fear aura that can be activated (do mummies get that? I think they might).
The argument was in the past that there aren't really any liches that could be able to or willing to teach and help a guy become a vassalich, but given recent quests (like Mephisto's "Sins of the Father" quest), I think the door could be opened for vassaliches on the server.
Would a developer be willing to try a hand at this? I know that the cons are quite obvious: I know aMPCs are time consuming to construct, and if we use the vampires as a base, then we're going to have some bug issues at first, but the pros are also quite obvious: liches and vassaliches are pretty wicked.