I'm currently preparing a Savage Worlds campaign based rather loosely on the setup from the PC/console game A Valley Without Wind. For those unfamiliar with AVWW, it's a post-magical-apocalyspe in which anyone exploring too far from the surviving village will be quickly killed by magical "fallout" from the apocalypse, unless they are a "glyphbearer" (i.e., a PC). AVWW has quasi-permadeath, in that, if you die, that character is dead and gone for good, but your "glyph" jumps to an NPC, allowing you to keep all the spells you've learned and continue play with the new character.
Although I've reskinned the names, this "glyph" business is one of the things I want to carry over into my game, but I'm unsure of how best to balance it.
My current thoughts are to define the glyph as a character in and of itself, albeit a very weak one - probably one attribute at d6, the rest at d4, player's choice of an Arcane Background, a d6 in the Arcane Background's skill, and that's it. The glyph would have to inhabit a host, which would be created as a normal Savage Worlds character and, on the body's death, the glyph transfers to a nearby henchman NPC.
The glyph will gain XP/advances/ranks very slowly (I want to say 1/5 normal rate, but that feels like it might be a bit too slowly) and players will always use the higher of either the glyph's or the host's abilities.
Has anyone else run a game with this sort of combined symbiote/host PCs before? Are there any suggestions for a better way to handle it mechanically?