Also, that might be way too OP for some combinations to even be permitted. Gozer with a Stand might not be so bad, and neither would, say, John with a Aura.
Give Mio a Semblance and an Aura, with her already powerful Mankai buff, and you have some potential issues.
Let me sort some things out and give a few examples...
Magic: most Undead cant use magic in any form (other then enchantments), that is a basic rule of undead, but Lichs, Vampires, Mummys, and spirits can, Why? because they have a Mind (Most of the time) and a Soul.
Soul: A Familier is a part of the Wisard's soul, And the mage takes the same damage it takes, which normally means death if the Familier dies and dismemberment if it is dismembered. This parallels with Stands, both take the same harm, one is just somewhat more benign in form.
For Magic: That depends on what you quantify as 'undead'. Garnt is an undead, but he can use magic, and he doesn't fit your categories; if anything, he's closest to a revenant. Magic also comes in different forms: I doubt somewhat that Alan can use Mankai, in the same way I doubt Mio could use his ice magic, because they are completely different things under the same name.
For Soul: Also not necessarily true. Familiars are basically sentient animals, Stands are personifications of fighting spirits. Different concepts, different ideas, and Familiars are not gained the same way, to boot. Also, the structure of a soul could basically be different as well across worlds, depending on what the lore states.
I'm personally going to champion not trying to combine stuff, as some of the lores you're going to attempt to combine really are incompatible.